URBAN FOREST RESOURCE ANALYSISforestry.nv.gov/.../01/Henderson-Resource-Analysis... · City of Henderson, Urban Forest Resource Analysis ii December 2013. Tables . Table 1. Population

URBAN FOREST RESOURCE ANALYSIS

City of Henderson, Nevada

January, 2013 Revised December, 2013

City of Henderson, Nevada Urban Forest Resource Analysis

January 2013

Prepared for: City of Henderson

Lisa Ortega Urban Forester

P.O. Box 95050, Mail Stop 411 702-267-4046

Prepared by: Davey Resource Group

A Division of The Davey Tree Expert Company 7627 Morro Rd.

Atascadero, California 93422 Phone: 805-461-7500

Toll Free: 800-966-2021 Fax: 805-461-8501 www.davey.com/drg

Acknowledgements

While the specific reports and recommendations can be attributed to this study, the basis for its structure and written content comes from the entire series of Municipal Forest Resource Analysis reports prepared and published by the USDA Forest Service, Pacific Southwest Research Station, Center for Urban Forest Research, and credit should be given to those authors. The Municipal Forest Resource Analysis Reports are companions to the regional Tree Guides and i-Tree’s STRATUM application developed by the USDA Forest Service, Pacific Southwest Research Station, Center for Urban Forest Research.

City of Henderson, Urban Forest Resource Analysis i December 2013

Table of Contents Executive Summary ....................................................................................................................... 1

Introduction .................................................................................................................................... 2

Chapter 1: Urban Forest Resource Summary ............................................................................ 4

Summary of Urban Forest Resource Structure ......................................................................... 4 Summary of Urban Forest Benefits ........................................................................................... 4 Urban Forest Resource Management ....................................................................................... 5

Chapter 2: Henderson’s Urban Forest Resource ...................................................................... 7

Population Composition ............................................................................................................. 7 Species Richness and Composition .......................................................................................... 8 Species Importance ................................................................................................................. 11 Canopy Cover .......................................................................................................................... 13 Relative Age Distribution ......................................................................................................... 13 Urban Forest Condition and Relative Performance................................................................. 16 Replacement Value ................................................................................................................. 18

Chapter 3: Urban Forest Resource Benefits ............................................................................ 21

Energy Savings ....................................................................................................................... 21 Electricity and Natural Gas Reduction ..................................................................................... 22 Atmospheric Carbon Dioxide Reduction ................................................................................. 24 Sequestered Carbon Dioxide .................................................................................................. 25 Air Quality Improvement .......................................................................................................... 27 Deposition and Interception ..................................................................................................... 27 Avoided Pollutants ................................................................................................................... 28 BVOC Emissions ..................................................................................................................... 28 Net Air Quality Improvement ................................................................................................... 28 Stormwater Runoff Reductions ................................................................................................ 30 Aesthetic, Property Value & Socioeconomic Benefits ............................................................. 32 Benefit Summary ..................................................................................................................... 34 Net Benefits and Benefit-Investment Ratio (BIR) .................................................................... 36

Conclusion .................................................................................................................................... 39 Appendix A: Methods and Procedures ..................................................................................... 41

Appendix B: References............................................................................................................. 42

Appendix C: Reports .................................................................................................................. 44

City of Henderson, Urban Forest Resource Analysis ii December 2013

Tables Table 1. Population Summary of Henderson’s Public Tree Inventory ............................................. 9

Table 2. Importance Value (IV) of Henderson’s Most Abundant Tree Species ............................. 12

Table 3. Relative Performance Index (RPI) for Henderson’s Most Abundant Public Tree Species ....................................................................................................................... 17

Table 4. Replacement Value of Henderson’s Most Common Public Tree Species....................... 19 Table 5. Annual Electric and Natural Gas Benefits from Henderson’s Tree Resource ................. 23

Table 6. Annual CO2 Reduction Benefits Provided by Henderson’s Public Tree Resource.......... 26

Table 7. Number of Exceedances of Federal Ground Level Ozone .............................................. 27

Table 8. Annual Air Quality Improvements Provided by Henderson’s Public Tree Resource ....... 29

Table 9 Annual Stormwater Runoff Reduction Benefits Provided by Henderson’s Public Tree Resource ........................................................................................................................................ 31 Table 10. Annual Property Value, Aesthetic, and Socioeconomic Benefits of Henderson’s Tree Resource ........................................................................................................................................ 33

Table 11. Summary of Average Current Annual Per Tree Related Benefits from Henderson’s Tree Resource .................................................................................................. 34

Table 12. Benefit Versus Investment Summary for Henderson’s Public Tree Resource .............. 38 Table 13. Henderson Benefit Prices Used In This Analysis .......................................................... 41

Figures Figure 1.Composition of Henderson’s Public Tree Population ........................................................ 7

Figure 2.Species Frequency in Henderson’s Public Tree Population ............................................. 8

Figure 3. Relative Age Distribution of Henderson's Public Trees .................................................. 14

Figure 4. Relative Age Distribution of Henderson’s Top Ten Public Tree Species ....................... 15

Figure 5. Overall Condition of Henderson’s Public Trees .............................................................. 16 Table 3. Relative Performance Index (RPI) for Henderson’s Most Abundant Public Tree Species ....................................................................................................................... 17

Figure 6. Annual Electricity and Natural Gas Benefits - Top 5 Species ........................................ 23

Figure 7. Annual Reduction of CO2 - Top 5 species ...................................................................... 25

Figure 8. Annual Improvement to Air Quality - Top 5 Species....................................................... 28

Figure 9. Annual Reduction in Stormwater Runoff - Top 5 Species .............................................. 30 Figure 10. Annual Increase in Property and Socioeconomic Values - Top 5 Species .................. 33

Figure 11. Summary of Annual per Tree Benefits from Henderson’s Most Prevalent Tree Species .................................................................................................................................. 35

City of Henderson, Urban Forest Resource Analysis 1 December 2013

Replacement of Henderson’s 25,753 public trees with trees of similar size, species, and condition would cost more

than $59 million.

Executive Summary Trees play a vital role in the community of Henderson, Nevada. They provide numerous benefits both tangible and intangible, to residents, visitors, and neighboring communities. Recognized as a Tree City, USA by the National Arbor Day Foundation since 1991, Henderson has demonstrated that public trees are a valued community resource, an important component of the urban infrastructure, and a part of the City’s identity.

With a proactive approach to managing the urban forest, the City of Henderson contracted with Davey Resource Group (DRG) in 2012 to collect an inventory of public trees in the City. The inventory included an inspection by a team of Certified Arborists who recorded information including species, size, condition, and current maintenance needs, as well as the geographic location of 25,753 individual tree sites. This inventory represents all city-managed trees. Upon completion of the inventory, DRG developed a detailed and quantified analysis of the current structure, function, and value of this tree resource using the inventory data in conjunction with i-Tree benefit-cost modeling software.

The analysis determined that Henderson’s public tree population is a cost-effective resource that provides annual benefits of $869,789 ($3.24 per capita). These benefits include energy savings, air quality improvements, stormwater interception, atmospheric CO2 reduction, and aesthetic contributions to the social and economic health of the community. Considering the annual investment of $304,139 ($1.13 per capita) to provide care for this resource, the community realizes an overall net benefit of $565,598. The bottom line is that for every $1 spent on public trees, the community of Henderson receives $2.86 in benefits.

Henderson’s public urban forest is reducing annual electric energy consumption by 1,221 megawatt hours (MWh) and annual natural gas consumption by 8,637 therms, for a combined value of $87,518 annually. In addition, these trees are removing 1.45 tons of pollutants from the air, including ozone (O3), nitrogen dioxide (NO2), and particulates (PM10) for an overall annual air quality benefit of $38,196. The tree canopy is reducing annual stormwater runoff volume by 7.68 million gallons, protecting local water resources by reducing sediment and pollution loading. Replacement of Henderson’s 25,753 public trees with trees of similar size, species, and condition would cost more than $59 million.

Trees are one community asset that has the potential to increase in value over time and with proper maintenance. Henderson’s public tree resource is a relatively young population in overall good condition. Moreover, although it is critical to maintain an adequate level of resources to protect this investment, with more than 127 different species, Henderson is well positioned to realize a significant increase in environmental services as this vital resource continues to mature. The City's ongoing commitment to maximizing and maintaining the benefits from its urban forest will ensure that the community continues to enjoy the richness of life afforded by Henderson.


The City of Henderson’s inventoried public tree resource is a relatively young population in overall good condition.

Introduction The City of Henderson, Nevada is located on the southeast fringe of the Las Vegas metro area. Encompassing an area of 105 square miles at an elevation of 1,867 feet above sea level, Henderson has a generally warm climate with an average rainfall of approximately four inches. The population, currently 268,300, has increased over 300% since 1990. Referred to as “the other side of southern Nevada”, the City of Henderson is nestled among three of the most renowned man-made attractions – the neon of Vegas, the engineering marvel of Hoover Dam, and the tranquil beauty of Lake Mead.

Individual trees and a healthy urban forest play important roles in the quality of life and the sustainability of Henderson. Research has demonstrated that healthy urban trees can improve the local environment and lessen the impact resulting from urbanization and industry (CUFR). Trees improve air quality by manufacturing oxygen and absorbing carbon dioxide (CO2), as well as filtering and reducing airborne particulate matter such as smoke and dust. Urban trees reduce energy consumption by shading structures from solar energy and reducing the overall rise in temperature created through urban heat island effects (EPA). Trees slow and reduce stormwater runoff, helping to protect critical waterways from excess pollutants and particulates. In addition, urban trees provide critical habitat for wildlife and promote a connection to the natural world.

In addition to these direct improvements, healthy urban trees increase the overall attractiveness of a community and have been proven to increase the value of local real estate by 7% to 10%, as well as promoting shopping, retail sales, and

tourism (Wolf, 2007). Trees support a more livable community, fostering psychological health and providing residents with a greater sense of place (Ulrich, 1986; Kaplan, 1989). Community trees, both public and private, soften the urban hardscape by providing a green sanctuary and making Henderson a more enjoyable place to live, work, and play. The City’s 25,753 inventoried public trees play a prominent role in the urban forest benefits afforded to the community and the citizens rely on the City of Henderson to protect and maintain this vital resource.

Acknowledged by the Arbor Day Foundation as a Tree City USA since 1991, there is ample evidence that Henderson values its trees. Reflecting appreciation, concern, and a proactive stance on the management of the community’s urban forest resource, the City contracted Davey Resource Group (DRG) to conduct an inventory of public tree assets. A team of ISA Certified Arborists mapped the location and collected data on publicly owned trees using global positioning system (GPS) technology. It is recommended that the resulting inventory data be maintained by the City's tree maintenance staff using an existing or dedicated asset management system to provide accurate and dependable inventory data specific to tree characteristics, health, and maintenance performed.


In addition to location, DRG arborists collected information about the species, size, condition, and current maintenance needs of each tree. The collected data was used in conjunction with i-Tree’s Streets, a STRATUM Analysis Tool (Streets v5.0.1; i-Tree v5.0.6), to develop a resource analysis and report of the current condition of the urban forest. This report, unique to Henderson, effectively quantifies the value of the community’s inventoried public trees in regards to actual benefits derived from the tree resource. In addition, the report provides baseline values that can be used when developing and updating an urban forest management plan. This helps in determining where to focus available resources and setting benchmarks for measuring progress. The inventory data collected for this report was collected from May, 2012 to October, 2013.

The purpose of the urban forest resource analysis and report is to provide information on the structure, function, and value of a specific tree resource. From this information, managers and citizens alike can make informed decisions about budgetary support and management priorities. This report provides the following information:

● A description of the current structure of Henderson’s public tree resource and an established benchmark for future management decisions.

● Current, detailed management expenditures for Henderson's publicly managed trees and critical baseline information for evaluating program efficiency.

● A quantified value of the environmental benefits provided by Henderson’s public trees illustrating the relevance and relationship of the resource to local quality of life issues such as air quality, environmental health, economic development, and psychological health.

● Data that may be used by resource managers in the pursuit of alternative funding sources and collaborative relationships with utility purveyors, non-governmental organizations, air quality districts, federal and state agencies, legislative initiatives, or local assessment fees.

● Benchmark data that can be used in the development of a long-term urban forest management plan.

Henderson’s urban forest inventory is a complete dataset of publicly managed trees in streets, parks, and City facilities. The inventory currently represents all of the city-managed trees.


Replacement of Henderson’s 25,753 public trees with trees of similar size, species, and condition would cost more

than $59 million.

Chapter 1: Urban Forest Resource Summary

Summary of Urban Forest Resource Structure The City of Henderson’s urban forest resource currently includes 25,753 publicly managed trees and 157 available planting sites. A structural analysis is the first step towards understanding the benefits provided by these trees as well as their management needs. Upon examination of species composition, diversity, age distribution, condition, canopy coverage, and replacement value, DRG determined that the following information characterizes Henderson’s inventoried public tree resource:

● Approximately 127 tree species were identified in the inventory. The predominant tree species is Pinus eldarica (Mondale pine, 9.9%), followed by Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, 8.7%) and Chilopsis linearis (Desert willow, 7.7%).

● The age structure of Henderson’s public tree population is very young, with 71.9% of trees measuring less than seven inches DBH (diameter at breast height, measured at 4’6” above the ground) and 26.2% measuring between 7 and 19 inches DBH.

● The majority of Henderson’s trees (73.2%) were determined to be in good condition, with an additional 23.0% graded fair. Maintaining the condition of existing trees for as long as possible will increase their useful lifespan and promote a steady flow of benefits to the community.

● Henderson’s public tree population has sequestered 3,750 tons of carbon (CO2), valued at approximately $56,243.

● Replacement of Henderson’s 25,753 public trees with trees of similar size, species, and condition would cost more than $59 million.

Summary of Urban Forest Benefits Annually, Henderson’s public trees provide cumulative benefits to the community at an average value of $33.78 per tree, for a total gross value of $869,789 per year. The City’s public trees are providing the following substantial annual benefits:

● Public trees reduce electricity and natural gas use in Henderson through shading and climate effects; a benefit totaling $1,221, an average of $3.40 per tree.

● The public trees in Henderson currently sequester 446 tons of atmospheric CO2 per year. An additional 610 tons is avoided through decreased energy use, resulting in a net value of $15,334 and an average of $0.60 per tree.

● Net air quality improvements provided by the public tree population through the removal and avoidance of air pollutants are valued at $38,196, an average per tree benefit of $1.48.

● Henderson public trees intercept an estimated 7.7 million gallons of stormwater annually for a total value of $36,857 per year, an average of $1.43 per tree.


Henderson receives $2.86 in benefits for every $1 invested on the public tree population

● The total annual benefits contributed by Henderson’s public trees to property value increases, aesthetics, and socioeconomic value are $691,883, an average of $26.87 per tree.

● When the City’s annual investment of $304,139 for maintenance of this urban forest resource is considered, the annual net benefit (benefits minus investment) to the City is $565,650. The average net benefit for an individual public tree in Henderson is $21.96 per year. In other words, Henderson receives $2.86 in benefits for every $1 invested on the public tree population.

Urban Forest Resource Management Henderson’s public tree population is a dynamic resource that is worth continued investment to maintain and extend its full benefit potential. The community forest is one of the few assets that has the potential to increase in value over time with proper management. Appropriate and timely tree care can substantially increase lifespan, preserving the higher benefit stream that results from a mature community forest. As individual trees continue to mature, and aging trees are replaced, the overall value of the community forest and the amount of benefits provided can be expected to increase as well. This vital, living resource is, however, vulnerable to a host of stressors and requires ecologically sound and sustainable best management practices to ensure a continued flow of benefits for future generations. With the benefit of a relatively young urban forest in good condition, Henderson can focus resources on maximizing the flow of benefits from the current tree population and maintaining a forward thinking approach. Based on the resource analysis, Davey Resource Group recommends the following:

● Work toward developing an appropriate age distribution. Henderson’s tree population is very heavily weighted toward small, young trees. This is likely indicative of the rapid growth Henderson has experienced in terms of human population over the last two decades. Henderson should work to offset this by implementing a nutrition-fertilization program to help maximize healthy tree growth.

● Maximize the benefits of the existing tree resource through comprehensive tree maintenance and a cyclical pruning schedule.

● Implement a structural pruning program for young and establishing trees to promote healthy structure, extend life expectancy, and reduce future costs and liability. This is especially important in the case of Henderson with such a large population of young trees.

● Continue to develop species diversity. While Henderson does not have any species comprising greater than 10% of the overall population, there are under-represented species and genera that Henderson could focus planting to improve overall diversity among its tree population.

● Maintain the inventory in an existing or newly purchased asset management system.

● Inventory the remainder of the urban forest, and update with new trees as they are planted.

The value of Henderson’s public tree resource should continue to increase as existing trees mature and new trees are planted. As the resource grows, continued investment in management


is critical to ensuring that residents will continue receiving a high return on investment in the future. It is not as simple as planting more trees to increase canopy cover and benefits. Planning and funding for tree care and tree management must complement planting efforts in order to ensure the long-term success and health of Henderson’s urban forest. Existing mature trees should be maintained and protected whenever possible since the greatest benefits accrue from the continued growth and longevity of the existing canopy. Since the City’s tree population is so young, the benefits provided by the more mature trees are even more pronounced. Henderson can take pride in knowing that street trees improve the quality of life in the City and that trees are well worth the investment.

This urban forest resource analysis and report, based on the current inventory status, defines the population and structure of Henderson’s public urban forest and quantifies the benefits of that resource. The analysis focuses solely on publicly owned, City-managed trees on streets, parks, and City facilities, using i-Tree Streets to establish baseline information on the value to the community. This report and the included analysis, which is unique to Henderson, effectively estimates and quantifies the value of these public tree assets in regards to actual benefits derived from this resource. In addition, the report provides a baseline analysis that can be used when creating, implementing, and updating an urban forest management plan, determining where best to focus available resources and setting benchmarks for measuring progress. An urban forest resource analysis provides information on the structure, function, and value of the urban forest and its assets so that forest managers and citizens alike can make informed decisions about budgetary support and management priorities. This report provides the following information:

● A description of the current structure of Henderson’s inventoried public urban forest resources, establishing a benchmark for future management decisions.

● Current, detailed management expenditures for Henderson’s public trees and critical baseline information for evaluating program efficiency.

● A quantified value of the environmental benefits provided by Henderson’s public urban forest, illustrating the relevance and relationship of the resource to local quality of life issues, such as air quality and environmental health, economic development, and psychological health.

● Quantified data that may be used by forest resource managers in the pursuit of alternative funding sources and collaborative relationships with utility managers, non-profit organizations, air quality districts, federal and state agencies, legislative initiatives, and/or in establishing or updating local assessment fees.

● Benchmark data that can be used in the development of a long-term urban and community forest management plan.


Chapter 2: Henderson’s Urban Forest Resource

Population Composition Broadleaf hardwood species dominate Henderson’s tree population, comprising 84.3% of the total inventory. Broadleaf trees typically have larger canopies than coniferous trees of the same size. Since many of the measurable benefits derived from trees are directly related to leaf surface area, broadleaf trees generally provide the highest level of benefits to a community. Larger-statured broadleaf tree species provide greater benefits than smaller-statured trees, independent of diameter (DBH). Deciduous broadleaf species make up 65% of Henderson’s public tree population, including 3% large-stature, 28% medium-stature, and 35% small-stature trees. Evergreen broadleaf trees comprise 19% of the population, including 1% large-stature, 8% medium-stature and 10% small-stature evergreen broadleaf trees. Large-stature conifers represent 13% of the overall population. Medium-statured palms make up 1% of the population, and small palms total 2%. Additional species total less than 1% of the population (Figure 1).

Figure 1.Composition of Henderson’s Public Tree Population

Broadleaf Deciduous Large

3%

Broadleaf Deciduous Medium

28%

Broadleaf Deciduous Small

35%

Broadleaf Evergreen Large

1%

Broadleaf Evergreen Medium

8%

Broadleaf Evergreen Small 10%

Conifer Evergreen Large 13%

Palm Medium 1% Palm Small

2%


Species Richness and Composition Henderson’s inventoried public tree population includes a mix of 127 species, significantly more than that of the mean of 53 species reported by McPherson and Rowntree (1989) in their nationwide survey of street tree populations in 22 U. S. cities.

The top ten species represent 58.3% of the total population (Figure 2 and Table 1). The predominant tree species are Pinus eldarica (Mondale pine, 9.9%), Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, 8.7%) and Chilopsis linearis (Desert willow, 7.7%).

There is a widely accepted rule that no single species should represent greater than 10% of the total population, while no single genus more than 20% (Clark Et al, 1997). In Henderson, no genus represents more than 20% of the population. The most prevalent genus is Prosopis (mesquite, 15.1%), followed by Fraxinus (ash) representing nearly 14.9% of the population. No species is more than 10% of the population, but Pinus eldarica and Fraxinus velutina ‘Fan-Tex’, which together make up almost 20% of the overall public tree population, come very close to exceeding the 10% species rule. A complete population summary can be found in Appendix C.

Figure 2.Species Frequency in Henderson’s Public Tree Population

Maintaining a diverse population within an urban forest is important. Dominance of any single species or genus can have detrimental consequences in the event of storms, drought, disease, pests, or other stressors that can severely affect an urban forest and the flow of benefits and costs over time. Catastrophic pathogens, such as Dutch Elm Disease (Ophiostoma ulmi), Emerald Ash Borer (Agrilus planipennis), Gold Spotted Oak Borer (GSOB) (Agrilus auroguttatus) Asian Longhorned Beetle (Anoplophora glabripennis), and Sudden Oak Death (SOD) (Phytophthora ramorum) are some examples of unexpected, devastating, and costly pests and pathogens that highlight the importance of diversity and the balanced distribution of species and genera.

Pinus eldarica 10%

Fraxinus velutina 'Fan-Tex'

9%

Chilopsis linearis 8%

Parkinsonia x 'Desert Museum'

6%

Acacia stenophylla

5% Quercus virginiana

4%

Prosopis glandulosa

4% Ulmus parvifolia 4%

Prosopis velutina 4%

Vitex agnus-castus

4%

Other Species 42%


Table 1. Population Summary of Henderson’s Public Tree Inventory

DBH Class (in)

Species 0-4 4-7 7-13 13-19

19-25

25-31

31-37

37-42 > 42 Total % of

Pop.

Broadleaf Deciduous Large (BDL) Gleditsia triacanthos 68 72 98 0 0 0 0 0 0 238 0.9 Populus fremontii 107 19 19 3 0 0 1 0 0 149 0.6 BDL Other 125 83 90 35 6 1 0 0 0 340 1.3 Total 300 174 207 38 6 1 1 0 0 727 2.8 Broadleaf Deciduous Medium (BDM) Fraxinus velutina 'Fan-Tex' 778 873 517 83 1 0 0 0 0 2,252 8.7 Ulmus parvifolia 578 288 155 46 1 0 0 0 0 1,068 4.1 Fraxinus velutina 369 214 258 68 3 1 0 0 0 913 3.5 Pistacia chinensis 351 221 272 26 0 0 0 0 0 870 3.4 Parkinsonia florida 221 222 149 27 2 0 0 0 0 621 2.4 Fraxinus angustifolia 181 171 159 47 2 0 0 0 0 560 2.2 Prosopis chilensis 116 107 79 16 1 0 0 0 0 319 1.2 Robinia pseudoacacia 44 111 55 5 0 0 0 0 0 215 0.8 BDM Other 121 54 64 34 22 12 7 0 0 315 1.2 Total 2,759 2,261 1,708 352 32 13 7 0 0 7,133 27.7 Broadleaf Deciduous Small (BDS) Chilopsis linearis 1,570 334 75 5 0 0 0 0 0 1,984 7.7 Parkinsonia x 'Desert Museum' 1,243 252 50 1 0 0 0 0 0 1,546 6.0 Prosopis glandulosa 846 156 89 12 0 0 0 0 0 1,103 4.3 Prosopis velutina 642 254 127 18 4 0 0 0 0 1,045 4.1 Vitex agnus-castus 852 75 7 0 0 0 0 0 0 934 3.6 Acacia farnesiana 576 185 78 21 2 0 0 0 0 863 3.4 Chiltalpa tashkentensis 148 289 145 9 0 0 0 0 0 591 2.3 Prosopis torreyana 91 59 33 6 1 0 0 0 0 190 0.7 Prosopis species 49 98 31 7 0 0 0 0 0 185 0.7 Prosopis pubescens 112 52 19 2 0 0 0 0 0 185 0.7 BDS Other 163 88 29 1 0 0 0 0 0 282 1.1 Total 6,292 1,842 683 82 7 0 0 0 0 8,908 34.6 Broadleaf Evergreen Large (BEL) Quercus ilex 66 11 0 0 0 0 0 0 0 77 0.3 Eucalyptus microtheca 69 1 1 3 0 0 0 0 0 74 0.3 Eucalyptus camaldulensis 6 2 5 0 2 0 0 0 0 15 0.1 Eucalyptus papuana 7 1 0 0 0 0 0 0 0 8 0.0 Quercus suber 1 1 1 0 0 0 0 0 0 3 0.0 Eucalyptus microcarpa 0 2 0 0 0 0 0 0 0 2 0.0 Eucalyptus spp. 0 0 1 0 0 0 0 0 0 1 0.0 Total 149 18 8 3 2 0 0 0 0 180 0.7 Broadleaf Evergreen Medium (BEM) Quercus virginiana 261 387 476 54 1 0 0 0 0 1,179 4.6 Prosopis alba 545 122 139 28 2 0 0 0 0 836 3.2 BEM Other 26 41 9 0 0 0 0 0 0 76 0.3 Total 832 550 624 82 3 0 0 0 0 2,091 8.1


Broadleaf Evergreen Small (BES) Acacia stenophylla 721 471 153 19 1 0 0 0 0 1,365 5.3 Sophora secundiflora 182 5 0 0 0 0 0 0 0 187 0.7 Acacia aneura 146 35 2 0 0 0 0 0 0 183 0.7 Olea europaea 38 80 47 2 0 0 0 0 0 167 0.6 Acacia greggii 143 17 2 1 0 0 0 0 0 163 0.6 BES Other 239 230 127 14 0 0 0 0 0 610 2.4 Total 1,469 838 331 36 1 0 0 0 0 2,675 10.4 Conifer Evergreen Large (CEL) Pinus eldarica 364 613 951 498 116 4 0 0 0 2,546 9.9 Pinus halepensis 2 13 158 311 66 10 1 0 0 561 2.2 Pinus roxburghii 2 8 50 71 8 0 0 0 0 139 0.5 Pinus pinea 0 2 10 2 0 0 0 0 0 14 0.1 Cupressus sempervirens 0 6 0 0 0 0 0 0 0 6 0.0 Total 368 642 1,169 882 190 14 1 0 0 3,266 12.7 Conifer Evergreen Medium (CEM) Pinus brutia 0 6 2 3 0 0 0 0 0 11 0.0 Cupressus glabra 3 2 3 1 0 0 0 0 0 9 0.0 Total 3 8 5 4 0 0 0 0 0 20 0.1 Conifer Evergreen Small (CES) Fouquieria splendens 0 0 0 0 0 0 0 1 0 1 0.0 Juniperus spp. 0 0 1 0 0 0 0 0 0 1 0.0 Total 0 0 1 0 0 0 0 1 0 2 0.0 Palm Evergreen Large (PEL) Phoenix canariensis 1 0 0 9 5 2 11 0 0 28 0.1 Trachycarpus fortunei 0 0 2 0 0 0 0 0 0 2 0.0 Total 1 0 2 9 5 2 11 0 0 30 0.1 Palm Evergreen Medium (PEM) Phoenix dactylifera 0 0 2 177 130 3 1 0 0 313 1.2 Total 0 0 2 177 130 3 1 0 0 313 1.2 Palm Evergreen Small (PES) Washingtonia robusta 0 5 46 236 15 0 0 0 0 302 1.2 Washingtonia filifera 0 1 10 28 21 24 2 3 0 89 0.3 Brahea armata 0 2 5 3 0 0 0 0 0 10 0.0 Butia capitata 0 0 0 4 0 0 0 0 0 4 0.0 Arecastrum romanzoffianum 0 0 3 0 0 0 0 0 0 3 0.0 Total 0 8 64 271 36 24 2 3 0 408 1.6 Grand Total 12,173 6,341 4,804 1,936 412 57 23 4 0 25,753 100%


Species Importance To quantify the significance of any one particular species found in Henderson’s inventoried public tree population, an importance value (IV) is derived for each of the most common species in the inventory. Importance values are particularly meaningful to urban forest managers because they indicate a community’s reliance on the functional capacity of particular species. i-Tree Streets calculates importance value based on the mean of three values: percentage of total population, percentage of total leaf area, and percentage of total canopy cover. Importance value goes beyond tree numbers alone to suggest reliance on specific species based on the benefits they provide. The importance value can range from zero (which implies no reliance) to 100 (suggesting total reliance). No single species should dominate the composition in the City’s urban forest population. Because importance value goes beyond population numbers alone, it can help managers to better comprehend the resulting loss of benefits from a catastrophic loss of any one species. When importance values are comparatively equal among the ten to 15 most abundant species, the risk of major reductions to benefits is significantly reduced. Of course, suitability of the dominant species is another important consideration. Planting short-lived or poorly adapted species can result in short rotations and increased long-term management costs.

The 21 most abundant species (>1% of the population) identified in Henderson’s public tree inventory represent 84.5% of the total population, 83.5% of the total leaf area, and 85.2% of the total canopy cover for a combined importance value of 84.4 (Table 2). Among these species, Henderson relies most on Pinus eldarica (Mondale pine, IV=13.02), followed by Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, IV=10.4).


Table 2. Importance Value (IV) of Henderson’s Most Abundant Tree Species

Species Number of Trees

% of Pop.

Leaf Area (ft2)

% of Total Leaf Area

Canopy Cover (ft2)

% of Total

Canopy Cover

Importance Value

Pinus eldarica 2,546 9.9 2,572,109 16.0 830,017 13.2 13.0 Fraxinus velutina 'Fan-Tex' 2,252 8.7 1,668,799 10.4 752,304 12.0 10.4 Chilopsis linearis 1,984 7.7 303,830 1.9 150,925 2.4 4.0 Parkinsonia x 'Desert Museum' 1,546 6.0 260,783 1.6 160,225 2.5 3.4

Acacia stenophylla 1,365 5.3 519,586 3.2 202,633 3.2 3.9 Quercus virginiana 1,179 4.6 920,161 5.7 402,300 6.4 5.6 Prosopis glandulosa 1,103 4.3 390,280 2.4 169,866 2.7 3.1 Ulmus parvifolia 1,068 4.1 1,020,052 6.3 485,561 7.7 6.1 Prosopis velutina 1,045 4.1 515,029 3.2 226,425 3.6 3.6 Vitex agnus-castus 934 3.6 120,467 0.7 78,848 1.3 1.9 Fraxinus velutina 913 3.5 796,559 4.9 254,610 4.0 4.2 Pistacia chinensis 870 3.4 590,630 3.7 257,874 4.1 3.7 Acacia farnesiana 863 3.4 223,564 1.4 123,518 2.0 2.2 Prosopis alba 836 3.2 285,820 1.8 70,343 1.1 2.0 Parkinsonia florida 621 2.4 426,041 2.6 253,566 4.0 3.0 Chiltalpa tashkentensis 591 2.3 250,603 1.6 132,041 2.1 2.0 Pinus halepensis 561 2.2 1,604,692 10.0 371,845 5.9 6.0 Fraxinus angustifolia 560 2.2 524,921 3.3 227,330 3.6 3.0 Prosopis chilensis 319 1.2 254,291 1.6 112,310 1.8 1.5 Phoenix dactylifera 313 1.2 95,524 0.6 68,974 1.1 1.0 Other trees 4,284 16.6 2,749,678 17.1 961,280 15.3 16.3

Total 25,753 100% 16,093,418 100% 6,292,795 100% 100%


An unevenly aged tree population assures continuity in overall tree canopy coverage and associated benefits

Canopy Cover The amount and distribution of leaf surface area is the driving force behind the urban forest’s ability to produce benefits for the community (Clark, 1997). As canopy cover increases, so do the benefits afforded by leaf area. It is important to remember that publicly managed street and park trees throughout the United States, including those in Henderson, likely represent less than 10% of the entire urban forest (Moll and Kollin, 1993). In Henderson, it is estimated that the public tree resource is providing approximately 144.5 acres of tree canopy cover.

Relative Age Distribution The distribution of individual tree ages within a tree population influences present and future costs as well as the flow of benefits. An unevenly aged population allows managers to allocate annual maintenance costs uniformly over many years and assures continuity in overall tree canopy coverage and associated benefits. A desirable distribution has a high proportion of young trees to

offset establishment and age related mortality as the percentage of older trees declines over time (Richards, 1982/83). This ideal, albeit uneven, distribution suggests a large fraction of trees (+/-40% of the total) should be young with diameters at breast height (DBH) less than eight inches, while only 10% should be in the large diameter classes (>24 inches).

Overall, the age distribution of Henderson’s inventoried public tree population is heavily weighted in young trees, with 71.9% of the population consisting of trees with a DBH (diameter at breast height) of seven inches or smaller and 27.8% established trees (8-25 inches DBH). Trees greater than 25 inches DBH make less than 1% of the overall population (Figure 3).

With continued, proactive management of this young urban forest, Henderson can expect greater benefits as this vital resource matures. New installations should carefully consider species selection, increasing the use of underutilized and well-performing species. In addition to planting, it is critical that long-term resources be dedicated to ensuring proper maintenance as trees mature. A long-term, sustainable management plan,

including regular inspection and reasonable pruning cycles, can ensure Henderson’s urban forest remains healthy and well-structured, thereby maximizing environmental services to the community, reducing risk, and promoting a consistent flow of benefits for many generations to come.


Figure 3. Relative Age Distribution of Henderson's Public Trees

Among Henderson’s top ten public tree species (Figure 4), seven have significant representation in the small size class (< 7 inches DBH), indicating that they are either very small stature trees, or recent plantings have focused on these species. Parkinsonia x ‘Desert Museum’ (Desert Museum palo verde, 97%), Prosopis glandulosa (Honey mesquite, 91%), Chilopsis linearis (desert willow, 97%), Prosopis velutina (velvet mesquite, 86%), Vitex agnus-castus (chaste tree, 99%), Acacia stenophylla (shoestring acacia, 87%), and Ulmus parvifolia (Chinese elm, 81%) are all significantly represented in the small size class. The age distributions of these species is partly a reflection of the fact that these are all small stature trees except for Ulmus parvifolia, which is medium-stature at maturity.

Considering large and medium-statured trees, only Pinus eldarica (Mondale pine, 0.2%) and Fraxinus velutina (velvet ash, 0.1%) have any representation (four trees and one tree, respectively) in the large class range (> 25" DBH). Although not among the top ten most numerous species, Pinus halepensis (Aleppo pine, 11 trees) and Morus alba (white mulberry, 18 trees) also have some large DBH trees.Pinus eldarica (Mondale pine, 61%) is a fairly well-established population with the greatest representation between 7 and 25 inches in diameter. Quercus virginiana (southern live oak, 40%) are weighted heavily in 7-13 inch size class and will grow to bolster the numbers in the medium size classes with adequate maintenance.

While none of Henderson’s top ten species demonstrate an age distribution indicative of a long-standing key species, Pinus eldarica comes the closest, with 38% of trees less than seven inches in diameter, 61% between 7 and 25 inches, and 0.2% greater than 24 inches. Considering this age distribution and that 82% of Pinus eldarica were rated as good during the inventory, this appears to be a species that is performing well for Henderson. However, as this species is on the threshold of over-representation in the Henderson urban forest (9.9%), future plantings would ideally expand other less-represented species.

It is important to keep in mind that, as these young populations mature and eventually age, their maintenance needs may increase. Future plantings should adequately represent long-standing and high-performing species, making sure to provide sufficient replacements to ensure the functional capacity and benefit streams from these populations, even as individuals begin to decline.

0 5

10 15 20 25 30 35 40 45 50 Citywide Total

Ideal

%

DBH Class (in)


Figure 4. Relative Age Distribution of Henderson’s Top Ten Public Tree Species

0

10

20

30

40

50

60

70

80

90 Pinus eldarica


Chilopsis linearis


Acacia stenophylla

Ideal

%

DBH Class (in)

0

10

20

30

40

50

60

70

80

90 Quercus virginiana

Prosopis glandulosa

Ulmus parvifolia

Prosopis velutina

Vitex agnus-castus

Ideal %

DBH Class (in)


Urban Forest Condition and Relative Performance Tree condition is an indication of how well trees are managed and how well they are performing in a given site-specific environment (e.g., street median, parking lot, etc.). Each inventoried tree was rated for overall condition, including consideration for structure, foliage, and the root collar. When trees are performing at their peak, as are 73% of Henderson’s inventoried trees classified as good, the benefits they provide are maximized.

The inventory found 23% of Henderson’s trees in fair condition, which may be an indication of age, inadequate resources or maintenance, and/or a poorly sited species, along with many other factors. Only 3.7% of the population was found to be in poor, dying, or dead condition. Removal or mitigation of dead and failing trees is recommended as soon as possible to reduce liability exposure.

The relative performance index (RPI) is one way to further analyze the condition and suitability of specific tree species. The RPI provides an urban forest manager with a detailed perspective on how one species’ performance compares to that of another. The index compares the condition ratings of each tree species with the condition ratings of every other tree species within a given urban forest population. An RPI value of 1.0 or better indicates that the species is performing as well or better than average when compared to other species. An RPI value below 1.0 indicates that the species is not performing as well in comparison to the rest of the population.

Among the 21 most common species (>1% of the total population) identified in the inventory, 12 have an RPI of 1.0 or greater (Table 3). Of these, Phoenix dactylifera (date palm) and Prosopis glandulosa (honey mesquite) have the highest RPI of 1.09 and 1.05, respectively. Chltalpa tashkentensis (Chitalpa) has the lowest rating of 0.89. Pinus eldarica (Mondale pine, RPI=1.04) is a population with a close to ideal age distribution, an indicator that the RPI value is a decent measure of performance.

Dead or Dying 0.8%

Poor 2.9%

Fair 23.0%

Good 73.2%

Figure 5. Overall Condition of Henderson’s Public Trees


Table 3. Relative Performance Index (RPI) for Henderson’s Most Abundant Public Tree Species

Species Dead or Dying Poor Fair Good RPI # of

Trees % of Pop.

Pinus eldarica 0.7 1.2 16.0 82.2 1.04 2,546 9.9 Fraxinus velutina 'Fan-Tex' 0.3 2.0 22.6 75.2 1.01 2,252 8.7 Chilopsis linearis 0.3 1.8 19.2 78.7 1.02 1,984 7.7 Parkinsonia x 'Desert Museum' 0.3 1.9 30.3 67.5 0.99 1,546 6.0 Acacia stenophylla 0.1 1.1 14.1 84.7 1.05 1,365 5.3 Quercus virginiana 1.1 5.2 25.0 68.7 0.98 1,179 4.6 Prosopis glandulosa 0.0 2.1 11.4 86.5 1.05 1,103 4.3 Ulmus parvifolia 0.4 4.3 44.1 51.2 0.93 1,068 4.1 Prosopis velutina 2.6 5.6 21.9 69.9 0.97 1,045 4.1 Vitex agnus-castus 0.5 1.3 16.1 82.1 1.04 934 3.6 Fraxinus velutina 2.1 3.7 39.1 55.1 0.93 913 3.5 Pistacia chinensis 0.2 0.9 14.3 84.6 1.05 870 3.4 Acacia farnesiana 0.3 1.6 28.6 69.4 0.99 863 3.4 Prosopis alba 0.8 2.3 30.6 66.3 0.98 836 3.2 Parkinsonia florida 3.2 2.7 29.0 65.1 0.96 621 2.4 Chiltalpa tashkentensis 0.2 6.4 51.1 42.3 0.89 591 2.3 Pinus halepensis 0.0 1.2 17.8 80.9 1.04 561 2.2 Fraxinus angustifolia 0.7 4.8 19.3 75.2 1.00 560 2.2 Prosopis chilensis 0.0 2.5 22.9 74.6 1.01 319 1.2 Phoenix dactylifera 0.0 0.0 2.6 97.4 1.09 313 1.2 Washingtonia robusta 0.7 6.0 1.7 91.7 1.05 302 1.2 Other trees 0.0 0.1 0.0 2.3 0.97 3,982 15.5 Citywide 0.8 2.9 23.0 73.2 1.00 25,753 100%

The RPI can be a useful tool for urban forestry managers. For example, if a city has been planting two or more new species in their urban forest, the RPI can be utilized to compare their relative performance. If the RPI indicates that one is performing relatively poorly, a municipality may decide to reduce or even stop planting that species and subsequently save money on both planting stock and replacement costs. The RPI enables managers to look at the performance of long-standing species as well. Species planted for many years that have an RPI of 1.00 or greater have performed well when compared to the population as a whole. These top performers should be retained as a significant portion of the urban forest population. It is important to keep in mind that, because RPI is based on condition, it may not reflect cosmetic or nuisance issues, especially seasonal issues that are not threatening the health or structure of the trees.

An RPI value less than 1.00 may be indicative of a species that is not well adapted to local conditions. Poorly adapted species are more likely to present increased safety and maintenance issues. Species with an RPI less than 1.00 should receive careful consideration before being selected for future planting choices. Prior to selecting or deselecting trees on the basis of RPI alone, managers are encouraged to take into account the age distribution of the species, among other factors. A species that has a RPI of less than 1.00, but has a significant number of trees in larger DBH classes, may just be exhibiting signs of population senescence. The individuals of this species may have produced substantial benefits over the years and should continue to be considered when making species selection determinations for future planting.

The RPI value can also be used to identify underutilized species that are demonstrating good performance. Trees with an RPI value greater than 1.00 and an established age distribution may


Replacement of the Mondale pine population in Henderson’s public

inventory would cost $11.7 million.

be indicating their suitability in the local environment and should receive consideration for additional planting. However, due to the size of the tree population sampled, the age class distribution for Henderson’s trees is not varied enough to allow for species performance decisions to be based solely on RPI values. Apart from existing species in Henderson, future tree plantings can enhance species diversity by adding new species with desert proven hardiness, including:

● Australian pine (Casuarina equisetifolia)

● Bottlebrush tree (Callistemon spp.)

● Kurrajong (Brachychiton populneus)

● Thornless cascalote (Caesalpinia cacalaco)

● Tipuana (Tipuana tipu)

Replacement Value The current value of Henderson’s public tree resource is approximately $59 million. The community forest is a public asset which, when properly cared for, has the potential to appreciate in value as the trees mature over time. Replacement value accounts for the historical investment in trees over their lifetime and is a way of describing the value of a tree population (and/or average value per tree) at a given time. Replacement value is a reflection of current population numbers, stature, placement, and condition. There are several methods available for obtaining a fair and reasonable perception of a tree’s value (CTLA, 1992; Watson, 2002). To determine the replacement value, species ratings, replacement costs, and basic prices were obtained for each species and input into the i-Tree software. To replace Henderson’s current inventoried public tree population of 25,753 trees with trees of similar size, species, and condition would cost more than $59 million (Table 5 and Appendix C). The average replacement value per tree is $2,303.

Pinus eldarica (Mondale pine) account for 19.7% ($11.7 million) of the total estimated replacement value, followed by Pinus halepensis (Aleppo pine, 12.2%, $7.2 million), and Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, 6.9%, $4 million). The high value of each of these species reinforces their importance to the City. Many of the highest valued species are large and medium-stature trees with large canopies and are therefore likely to have high importance values (IV) as well.

Species with lower replacement values are generally smaller-stature trees with a lower IV, as evidenced by Vitex agnus-castus (chaste tree) with a replacement value of $452,395 (0.8%), or the easily replaced Washingtonia robusta (Mexican fan palm) with a replacement value of $148,134 (0.3%).

Henderson’s urban forest is a vital component of the City’s infrastructure and a public asset valued at approximately $59 million—an asset that, with proper care and maintenance, will increase in value over time. Distinguishing replacement value from the value of annual benefits produced by Henderson’s public trees is very important. Annual benefits are discussed in Chapter 3.


Table 4. Replacement Value of Henderson’s Most Common Public Tree Species

DBH Class (in) Species 0-4 4-7 7-13 13-19 19-25 25-31 31-37 37-42 > 42 Total % of Total $ Pinus eldarica 100,287 756,601 3,696,338 4,933,176 2,097,624 117,204 0 0 0 11,701,229 19.7 Pinus halepensis 709 19,839 838,567 4,211,412 1,727,949 385,521 62,523 0 0 7,246,521 12.2 Fraxinus velutina 'Fan-Tex' 213,637 1,070,878 2,006,424 782,280 13,659 0 0 0 0 4,086,877 6.9

Quercus virginiana 77,504 618,521 2,488,597 745,674 27,024 0 0 0 0 3,957,320 6.7 Pistacia chinensis 135,618 486,740 1,869,800 473,274 0 0 0 0 0 2,965,432 5.0 Acacia stenophylla 244,772 810,296 818,490 251,654 27,024 0 0 0 0 2,152,236 3.6 Ulmus parvifolia 167,696 447,545 796,404 592,824 27,024 0 0 0 0 2,031,493 3.4 Prosopis velutina 231,593 515,095 833,159 309,740 128,588 0 0 0 0 2,018,176 3.4 Parkinsonia florida 82,426 447,365 916,091 394,215 59,191 0 0 0 0 1,899,289 3.2 Fraxinus velutina 74,686 202,434 756,164 502,819 36,801 17,389 0 0 0 1,590,292 2.7 Chiltalpa tashkentensis 49,402 533,909 857,098 127,795 0 0 0 0 0 1,568,204 2.6

Chilopsis linearis 526,278 541,300 368,086 54,891 0 0 0 0 0 1,490,554 2.5 Prosopis glandulosa 335,971 319,431 593,343 188,443 0 0 0 0 0 1,437,188 2.4

Acacia farnesiana 222,188 344,696 485,618 327,068 48,986 0 0 0 0 1,428,556 2.4 Fraxinus angustifolia 50,546 203,812 599,098 441,737 38,699 0 0 0 0 1,333,892 2.2

Parkinsonia x 'Desert Museum' 460,568 506,494 297,099 12,996 0 0 0 0 0 1,277,158 2.2

Phoenix dactylifera 0 0 5,940 631,018 468,127 9,744 3,601 0 0 1,118,430 1.9 Prosopis alba 149,947 141,623 475,797 233,896 33,008 0 0 0 0 1,034,271 1.7 Pinus roxburghii 439 7,354 155,219 546,355 117,582 0 0 0 0 826,949 1.4 Morus alba 393 576 2,374 106,788 227,932 190,959 151,253 0 0 680,275 1.1 Prosopis chilensis 32,794 133,322 292,054 131,491 19,350 0 0 0 0 609,011 1.0 Olea europaea 13,510 162,605 313,771 36,822 0 0 0 0 0 526,708 0.9 Prosopis torreyana 35,568 128,740 224,855 88,807 34,698 0 0 0 0 512,668 0.9 Gleditsia triacanthos 14,764 84,430 387,069 0 0 0 0 0 0 486,264 0.8

Vitex agnus-castus 285,116 127,459 39,820 0 0 0 0 0 0 452,395 0.8 Robinia pseudoacacia 12,025 128,058 176,490 36,357 0 0 0 0 0 352,929 0.6


DBH Class (in) Species 0-4 4-7 7-13 13-19 19-25 25-31 31-37 37-42 > 42 Total % of Total $ Prosopis species 11,895 106,654 109,279 59,989 0 0 0 0 0 287,816 0.5 Platanus wrightii 12,239 0 60,171 82,288 82,577 17,389 0 0 0 254,664 0.4 Pyrus kawakamii 0 62,134 122,334 58,777 0 0 0 0 0 243,245 0.4 Chamaerops humilis 709 85,221 56,886 71,781 0 0 0 0 0 214,597 0.4

Prosopis pubescens 31,737 67,016 78,091 20,602 0 0 0 0 0 197,446 0.3 Fouquieria splendens 0 0 0 0 0 0 0 0 196,994 196,994 0.3

Yucca brevifolia 0 27,945 117,788 28,712 0 0 0 0 0 174,445 0.3 Fraxinus uhdei 1,614 19,310 78,889 71,651 0 0 0 0 0 171,465 0.3 Olneya tesota 4,594 14,955 108,609 41,270 0 0 0 0 0 169,427 0.3 Rhus lancea 18,429 47,357 101,726 0 0 0 0 0 0 167,511 0.3 Washingtonia robusta 0 1,389 21,941 118,246 6,557 0 0 0 0 148,134 0.2

Other trees 370,573 570,686 775,112 381,799 62,032 37,135 95,739 3,480 0 2,296,554 3.9 Citywide Total $3,970,227 $9,741,792 $21,924,589 $17,096,647 $5,284,434 $775,341 $313,116 $3,480 $196,994 $59,306,619 100%


Trees and other vegetation within an urbanized environment help reduce the urban heat island effect

Chapter 3: Urban Forest Resource Benefits Trees are important to the City of Henderson. Environmentally, they help conserve and reduce energy use, reduce local and global carbon dioxide (CO2) levels, improve air quality, and mitigate stormwater runoff. Additionally, trees provide a wealth of well-documented psychological, social,

and economic benefits related primarily to their aesthetic effects. Environmentally, trees make good sense, working ceaselessly to provide benefits back to the community. However, the question remains, are the collective benefits worth the costs of management? In other words, are trees a good investment for Henderson? To answer this question, the benefits must be quantified in financial terms. This analysis provides a snapshot of the annual benefits (along with the value of those benefits) produced by Henderson’s inventoried public urban forest. While the annual benefits produced by the urban forest can be substantial, it's important to recognize that the greatest benefits from the urban forest are derived from the benefit stream that results over a greater period of time from a mature forest where trees are well managed, healthy, and long-lived.

This analysis-utilized Henderson’s current public tree

inventory and i-Tree’s Streets model to assess and quantify the beneficial functions of this public tree resource and to place a dollar value on the annual environmental benefits these trees provide. These

estimates provide first-order approximations of tree value. While i-Tree Streets only generally accounts for the benefits produced by Henderson’s public tree population, it is an accounting based on the best available and current scientific research with an accepted degree of uncertainty. The data returned from i-Tree Streets can provide a platform from which management decisions can be made (Maco and McPherson, 2003). A discussion on the methods used to quantify and put a monetary value on these benefits can be found in Appendix A.

Energy Savings Trees modify climate and conserve energy in three principal ways:

● Shading reduces the amount of radiant energy absorbed and stored by hardscape surfaces, thereby reducing the heat island effect.

● Transpiration converts moisture to water vapor, thereby cooling the air by using solar energy that would otherwise result in heating of the air.

● Reduction of wind speed and the movement of outside air into interior spaces and conductive heat loss where thermal conductivity is relatively high (e.g., glass windows) (Simpson, 1998).

Heat island effect describes the increase in urban temperatures in relation to surrounding locations and is associated with an increase in hardscape and impervious surfaces. Trees and


other vegetation within an urbanized environment help reduce the heat island effect by lowering air temperatures 5°F (3°C) compared with outside the green space (Chandler, 1965). On a larger citywide scale, temperature differences of more than 9°F (5°C) have been observed between city centers without adequate canopy coverage and more vegetated suburban areas (Akbari and others, 1992). The relative importance of these effects depends upon the size and configuration of trees and other landscape elements (McPherson, 1993). Tree spacing, crown spread, and vertical distribution of leaf area each influence the transport of warm air and pollutants along streets and out of urban canyons.

By reducing air movement into buildings and against conductive surfaces (e.g., glass, metal siding), trees reduce conductive heat loss from buildings. Trees can reduce wind speed and the resulting air infiltration by up to 50%, translating into potential annual heating savings of 25% (Heisler, 1986).

Electricity and Natural Gas Reduction Electricity and natural gas saved annually in Henderson from both the shading and climate effects of public trees is equal to 1,221 MWh ($87,518) and 8,637 therms ($5,575), for a total retail savings of approximately $87,518 and an average of $3.40 per tree (Table 6). Pinus eldarica (Mondale pine), which represents 9.9% of the population with an importance value of 13.0, accounts for 14% of the total energy savings. Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, 11.7%) provides the next greatest contribution towards total energy savings, mostly due in part to canopy size and prevalence within the overall population.

Quercus virginiana (southern live oak), which represents 4.6% of the total population, is contributing 6.4% of the total energy savings because of the relatively young age distribution of this population (55% of trees <7” DBH). As this population of medium-stature trees matures, the energy benefits can be expected to increase substantially.

Examining average energy savings on a per tree basis (Figure 6), Pinus halepensis (Aleppo pine, $9.22) is currently the greatest contributor, primarily due to their relatively mature age distribution as compared to the rest of the tree population. Small-stature trees, such as Prosopis alba (South American mesquite, $1.27) and Chilopsis linearis (desert willow, $1.03), are contributing energy-saving benefits well below the average of $3.40. Although each of these populations has a young age distribution, neither species matures with a substantial canopy, consequently their contribution to energy savings will not increase substantially as they age. While these species are recommended for future plantings, this is based on their relative performance in terms of condition. If Henderson wishes to increase the benefits of energy savings from their urban tree population, consideration should be given to larger stature trees that have an increased performance in terms of shading and wind reduction.


Figure 6. Annual Electricity and Natural Gas Benefits - Top 5 Species

Table 5. Annual Electric and Natural Gas Benefits from Henderson’s Tree Resource

Species Total

Electricity (MWh)

Electricity ($)

Total Natural

Gas (Therms)

Natural Gas ($) Total ($) % of

Pop. % of

Total $ Avg.

$/tree

Pinus eldarica 171.9 11,535 1,078.8 696.4 12,231 9.9 14.0 4.80 Fraxinus velutina 'Fan-Tex' 142.8 9,580 1,022.0 659.7 10,239 8.7 11.7 4.55

Chilopsis linearis 28.1 1,884 239.6 154.7 2,038 7.7 2.3 1.03 Parkinsonia x 'Desert Museum' 29.6 1,984 252.7 163.1 2,147 6.0 2.5 1.39

Acacia stenophylla 38.2 2,566 297.2 191.8 2,758 5.3 3.2 2.02 Quercus virginiana 78.8 5,288 538.8 347.8 5,636 4.6 6.4 4.78 Prosopis glandulosa 31.7 2,129 242.4 156.5 2,286 4.3 2.6 2.07 Ulmus parvifolia 90.4 6,063 582.3 375.9 6,439 4.2 7.4 6.03 Prosopis velutina 42.4 2,846 314.1 202.8 3,049 4.1 3.5 2.92 Vitex agnus-castus 14.3 960 127.3 82.2 1,042 3.6 1.2 1.12 Fraxinus velutina 50.2 3,366 365.4 235.9 3,602 3.6 4.1 3.94 Pistacia chinensis 49.8 3,345 360.5 232.7 3,577 3.4 4.1 4.11 Acacia farnesiana 23.1 1,553 187.0 120.7 1,674 3.4 1.9 1.94 Prosopis alba 14.8 993 100.7 65.0 1,058 3.3 1.2 1.27 Parkinsonia florida 47.3 3,175 329.1 212.4 3,387 2.4 3.9 5.45 Chiltalpa tashkentensis 25.3 1,701 195.6 126.3 1,827 2.3 2.1 3.09 Pinus halepensis 72.8 4,884 447.8 289.0 5,173 2.2 5.9 9.22 Fraxinus angustifolia 43.0 2,887 298.7 192.8 3,079 2.2 3.5 5.50 Prosopis chilensis 21.3 1,427 150.4 97.1 1,524 1.2 1.7 4.78 Phoenix dactylifera 12.3 826 108.5 70.1 896 1.2 1.0 2.86 Washingtonia robusta 5.3 353 44.5 28.7 382 1.2 0.4 1.26 Other trees 187.8 12,602 1,353.1 873.5 13,475 15.5 15.4 3.38

CITYWIDE TOTAL 1,221 $81,943 8,637 $5,575 $87,518 100% 100% $3.40

$0 $2 $4 $6 $8 $10

Pinus halepensis

Ulmus parvifolia

Fraxinus angustifolia

Parkinsonia florida

Pinus eldarica

$9.22

$6.03

$5.50

$5.45

$4.80


Henderson’s public trees provide air quality improvements and a significant reduction in atmospheric carbon dioxide.

Atmospheric Carbon Dioxide Reduction As environmental awareness continues to increase, governments are paying particular attention to global warming and the effects of greenhouse gas emissions. Two national policy options are currently under debate, the establishment of a carbon tax and a greenhouse gas cap-and-trade system, aimed at the reduction of atmospheric carbon dioxide (CO2) and other greenhouse gases. A carbon tax would place a tax burden on each unit of greenhouse gas emission and would require regulated entities to pay for their level of emissions. Alternatively, in a cap-and-trade system, an upper limit (or cap) is placed on global (federal, regional, or other jurisdiction) levels of greenhouse gas emissions and the regulated entities would be required to either reduce emissions to required limits or purchase emissions allowances in order to meet the cap (Williams and others, 2007). The concept of purchasing emission allowances (offsets) has led to the acceptance of carbon credits as a commodity that can be exchanged for financial gain. The Center for Urban Forest Research (CUFR, Pacific Southwest Research Station, and USDA Forest Service) recently led the development of Urban Forest Project Reporting Protocol. The protocol, which incorporates methods of the Kyoto Protocol and Voluntary Carbon Standard (VCS), establishes methods for calculating reductions, provides guidance for accounting and reporting, and guides urban forest managers in developing tree planting and stewardship projects that could be registered for greenhouse gas (GHG) reduction credits (offsets). The protocol can be applied to urban tree planting projects within municipalities, campuses, and utility service areas anywhere in the United States.

While Henderson’s urban forest resource may or may not qualify for carbon-offset credits or be traded in the open market, the City’s public trees are nonetheless providing a significant reduction in atmospheric carbon dioxide (CO2) for a positive environmental and financial benefit to the community.

Urban trees reduce atmospheric carbon dioxide (CO2) in two ways:

● Directly, through growth and the sequestration of CO2 as wood and foliar biomass

● Indirectly, by lowering the demand for heating and air conditioning, thereby reducing the emissions associated with electric power generation and natural gas consumption.

Conversely, CO2 is released by vehicles and other combustible engines used to plant and care for trees. Additionally, when a tree dies, most of the CO2 that accumulated as woody biomass is released back into the atmosphere during decomposition, except in cases where the wood is


recycled. Each of these factors must be considered when calculating the CO2 reduction benefits of trees.

Sequestered Carbon Dioxide To date, Henderson’s inventoried public urban forest has sequestered a total of 3,750 tons of carbon dioxide (CO2) valued at $56,2431. Annually, this tree resource directly sequesters 448 tons of CO2, valued at $6,715, into woody and foliar biomass. Accounting for estimated CO2 emissions from tree decomposition (-30 tons), tree related maintenance activity (-5.7 tons), and avoided CO2 (610 tons), Henderson’s trees provide an annual net reduction in atmospheric CO2 of 1,022 tons, valued at $15,334 with an average of $0.60 per tree (Table 7).

Pinus halepensis (Aleppo pine, $1.74) and Quercus virginiana (southern live oak, $1.33) are currently providing the highest per tree benefit (Figure 7).

Pinus eldarica (Mondale pine) are providing the greatest percentage of overall benefits at 12.2% due to their prevalence in the population and large stature (just $0.74 per tree).

Figure 7. Annual Reduction of CO2 - Top 5 species

1 Based on i-Tree Streets default value of $15 per ton. Market value may vary.

$0.00 $0.50 $1.00 $1.50 $2.00

Pinus halepensis

Quercus virginiana


Ulmus parvifolia

Parkinsonia florida

$1.74

$1.33

$0.91

$0.88

$0.87

City of Henderson, Urban Forest Resource Analysis December 2013

Table 6. Annual CO2 Reduction Benefits Provided by Henderson’s Public Tree Resource

Species Sequestered (lb)

Sequestered ($)

Decomposition Release(lb)

Maintenance Release (lb)

Total Release

($) Avoided (lb) Avoided

($) Net Total (lb) Total ($) % of Pop.

% of Total $

Avg. $/tree

Pinus eldarica 91,136 684 -11,075 -1,889 -97.23 171,821 1,288.65 249,993 1,874.94 9.9 12.2 0.74 Fraxinus velutina 'Fan-Tex' 89,970 675 -4,133 -1,010 -38.57 142,692 1,070.19 227,519 1,706.39 8.7 11.1 0.76

Chilopsis linearis 14,074 106 -74 -456 -3.97 28,056 210.42 41,600 312.00 7.7 2.0 0.16 Parkinsonia x 'Desert Museum' 31,642 237 -1,288 -344 -12.24 29,547 221.60 59,558 446.68 6.0 2.9 0.29

Acacia stenophylla 14,236 107 -742 -462 -9.02 38,220 286.65 51,253 384.40 5.3 2.5 0.28 Quercus virginiana 137,092 1,028 -6,745 -650 -55.47 78,767 590.75 208,463 1,563.47 4.6 10.2 1.33 Prosopis glandulosa 22,831 171 -766 -285 -7.88 31,713 237.85 53,494 401.20 4.3 2.6 0.36 Ulmus parvifolia 38,196 286 -2,346 -396 -20.56 90,313 677.35 125,767 943.26 4.2 6.2 0.88 Prosopis velutina 28,639 215 -1,171 -339 -11.32 42,396 317.97 69,525 521.44 4.1 3.4 0.5 Vitex agnus-castus 14,381 108 -431 -171 -4.52 14,296 107.22 28,074 210.56 3.6 1.4 0.23 Fraxinus velutina 41,855 314 -2,532 -445 -22.33 50,133 376.00 89,012 667.59 3.6 4.4 0.73 Pistacia chinensis 21,037 158 -1,546 -396 -14.57 49,820 373.65 68,914 516.86 3.4 3.4 0.59 Acacia farnesiana 26,509 199 -1,659 -258 -14.38 23,132 173.49 47,724 357.93 3.4 2.3 0.42 Prosopis alba 15,402 116 -1,563 -286 -13.86 14,791 110.93 28,344 212.58 3.3 1.4 0.25 Parkinsonia florida 26,189 196 -1,286 -284 -11.78 47,288 354.66 71,907 539.30 2.4 3.5 0.87 Chiltalpa tashkentensis 31,158 234 -2,049 -272 -17.41 25,336 190.02 54,173 406.30 2.3 2.7 0.69

Pinus halepensis 63,700 478 -5,465 -658 -45.92 72,744 545.58 130,321 977.41 2.2 6.4 1.74 Fraxinus angustifolia 26,531 199 -1,456 -289 -13.09 42,999 322.49 67,784 508.38 2.2 3.3 0.91 Prosopis chilensis 13,322 100 -663 -148 -6.08 21,252 159.39 33,763 253.22 1.2 1.7 0.79 Phoenix dactylifera 5,115 38 -1,430 -221 -12.38 12,298 92.24 15,762 118.22 1.2 0.8 0.38 Washingtonia robusta 7,333 55 -1,813 -333 -16.10 5,262 39.47 10,449 78.37 1.2 0.5 0.26

Other trees 135,006 1,013 -9,759 -1,767 -86.45 187,710 1,407.83 311,190 2,333.92 15.5 15.2 0.59

CITYWIDE TOTAL 895,354 $6,715 -59,992 -11,359 -$535.14 1,220,586 $9,154 2,044,589 $15,334 100% 100% $0.60


Year Ozone > Federal 2012 8-hour Standard

2012 19

2011 9

2010 1

2009 5

2008 10

2007 17

2006 8

2005 8

2004 4

2003 10

Average 9.1

Air Quality Improvement Urban trees improve air quality in five fundamental ways:

● Absorption of gaseous pollutants such as ozone (O3) and nitrogen dioxide (NO2) through leaf surfaces,

● Interception of particulate matter (PM10), such as dust, ash, dirt, pollen, and smoke,

● Reduction of emissions from power generation by reducing energy consumption,

● Increase of oxygen levels through photosynthesis, and

● Transpiration of water and shade provision, resulting in lower local air temperatures, thereby reducing ozone (03) levels.

According to data reported by the Clark County Department of Air Quality, air quality in Henderson exceeded the state 24-hour standard of 150 μg/m3 for PM10 only 1 day in 2012.

Between 2003 and 2012 there have been 91 exceedances of the Federal 8-hour standard for ground level ozone ((03), an average of 9.1 days per year (Table 7).

In the absence of cooling effects provided by trees, higher temperatures contribute to ozone (O3) formation. Additionally, short-term increases in ozone concentrations have been statistically associated with increased tree mortality for 95 large US cities (Bell and others, 2004). However, it should be noted that while trees do a great deal to absorb air pollutants (especially ozone and particulate matter), they also negatively contribute to air pollution. Trees emit various biogenic volatile organic compounds (BVOCs), such as isoprenes and monoterpenes, which can also contribute to ozone formation. These BVOC emissions are accounted for by i-Tree Streets in the air quality net benefit.

Deposition and Interception Each year, approximately 1.9 tons of nitrogen dioxide (NO2), small particulate matter (PM10), and ozone (O3) are intercepted or absorbed by the public trees in Henderson, for a value of $19.590 (Table 9). As a population, Pinus eldarica (Mondale pine, 783 lbs.), Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, 371 lbs.), and Ulmus parvifolia (Chinese elm, 256 lbs.) are the greatest contributors to air quality improvements, accounting for nearly half (38%) of total deposition benefits.

Table 7. Number of Exceedances of Federal Ground Level Ozone


Avoided Pollutants By reducing energy needs, the energy savings provided by trees have the additional indirect benefit of reducing air pollutant emissions (NO2, PM10, SO2, and VOCs) that result from energy production. Altogether, 2.1 tons of pollutants, valued at $38,728, are avoided annually through the shading effects of Henderson’s public trees. The populations of Pinus eldarica (Mondale pine, 589 lbs.), Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash, 488 lbs.), Ulmus parvifolia (Chinese elm, 308 lbs.) and Quercus virginiana (southern live oak, 270 lbs.) provide a combined 40% of the total benefits and have the greatest impact on reducing energy needs and therefore avoiding the additional generation of pollutants.

BVOC Emissions Biogenic volatile organic compound (BVOC) emissions from trees, which negatively affect air quality, must also be considered. Approximately 2.5 tons of BVOCs are annually emitted from Henderson’s public trees, offsetting the total air quality benefit by -$20,120. Quercus virginiana (southern live oak) are the heaviest per tree emitters of BVOCs (1.62 lbs. per tree), accounting for 38% of the total BVOC emissions, while representing only 4.6% of the total population. Ultimately, Quercus virginiana has a negative net impact on air quality of -$3.48 per tree.

Net Air Quality Improvement Net air pollutants removed, avoided, and released by Henderson’s inventoried public tree population are valued at $38,187 annually. The average net benefit per tree is $1.48. Trees vary dramatically in their ability to produce net air quality benefits. Typically, large-canopied trees with large leaf surface areas that are not high emitters of BVOCs produce the greatest benefits. On a per tree basis, Pinus halepensis (Aleppo pine, $4.14) and Ulmus parvifolia (Chinese elm, $3.91) currently produce the greatest per tree net air quality improvements (Figure 8).

Figure 8. Annual Improvement to Air Quality - Top 5 Species

$0 $3 $5

Pinus halepensis

Ulmus parvifolia

Pinus eldarica


Parkinsonia florida

$4.14

$3.91

$3.31

$3.12

$2.99


Table 8. Annual Air Quality Improvements Provided by Henderson’s Public Tree Resource

Species Deposition O3 (lb)

Deposition NO2 (lb)

Deposition PM10 (lb)

Deposition SO2 (lb)

Total Deposition

($)

Avoided NO2 (lb)

Avoided PM10

(lb)

Avoided VOC (lb)

Avoided SO2 (lb)

Total Avoided

($)

BVOC Emissions

(lb)

BVOC Emissions ($)

Total (lb) Total ($) % of Pop.

Avg. $/tree

Pinus eldarica 295.3 161.1 294.6 32.48 4,102.99 307.5 15.7 2.7 263.3 5,469.4 -286.03 -1,144.1 1,086.6 8,428.27 9.9 3.31 Fraxinus velutina 'Fan-Tex' 140.3 67.4 149.6 13.96 1,947.49 254.9 13.0 2.3 217.8 4,526.2 -236.73 -946.9 622.6 5,526.84 8.7 2.45

Chilopsis linearis 15.6 4.3 14.5 0.95 181.34 50.3 2.6 0.5 42.8 890.9 -202.56 -810.3 -71.1 261.99 7.7 0.13 Parkinsonia x 'Desert Museum' 29.0 14.0 31.1 2.89 404.04 53.0 2.7 0.5 45.1 938.8 -108.12 -432.5 70.2 910.34 6.0 0.59

Acacia stenophylla 33.2 18.1 39.5 3.65 499.30 68.4 3.5 0.6 58.3 1,213.0 0.00 0.0 225.2 1,712.28 5.3 1.25 Quercus virginiana 69.5 37.9 81.9 7.66 1,041.48 141.2 7.2 1.3 120.7 2,508.4 -1,913.37 -7,653.5 -1,446.0 -4,103.63 4.6 -3.48 Prosopis glandulosa 25.0 12.0 28.5 2.49 357.62 56.7 2.9 0.5 48.4 1,005.9 -55.36 -221.5 121.0 1,142.09 4.3 1.04 Ulmus parvifolia 108.4 41.9 96.9 8.69 1,319.18 160.8 8.2 1.4 137.5 2,857.6 0.00 0.0 563.9 4,176.83 4.1 3.91 Prosopis velutina 39.0 18.7 42.4 3.88 546.62 75.7 3.9 0.7 64.6 1,343.0 -73.06 -292.2 175.8 1,597.36 4.1 1.53 Vitex agnus-castus 10.4 5.0 12.3 1.04 151.80 25.6 1.3 0.2 21.8 453.7 -49.95 -199.8 27.8 405.74 3.6 0.43 Fraxinus velutina 47.1 18.2 44.6 3.78 588.10 90.1 4.6 0.8 76.9 1,599.0 0.00 0.0 286.1 2,187.10 3.5 2.40 Pistacia chinensis 85.5 33.1 70.8 6.86 1,006.58 89.4 4.6 0.8 76.3 1,586.8 -542.64 -2,170.5 -175.3 422.86 3.4 0.49 Acacia farnesiana 34.3 16.5 33.1 3.41 455.47 41.7 2.1 0.4 35.6 740.1 -92.69 -370.8 74.5 824.80 3.3 0.96 Prosopis alba 13.8 7.5 15.6 1.52 202.27 26.7 1.4 0.2 22.9 474.8 -80.25 -321.0 9.3 356.04 3.2 0.43 Parkinsonia florida 63.6 30.6 62.9 6.32 853.11 84.3 4.3 0.8 72.0 1,497.1 -123.93 -495.7 200.8 1,854.49 2.4 2.99 Chiltalpa tashkentensis 42.5 20.4 39.8 4.22 557.18 45.5 2.3 0.4 38.8 807.0 -103.90 -415.6 90.2 948.60 2.3 1.61

Pinus halepensis 55.4 30.2 68.4 6.10 849.03 128.6 6.6 1.1 110.1 2,287.4 -203.03 -812.1 203.6 2,324.27 2.2 4.14 Fraxinus angustifolia 50.3 24.2 51.2 5.00 683.75 76.6 3.9 0.7 65.5 1,361.2 -74.46 -297.8 203.0 1,747.12 2.2 3.12 Prosopis chilensis 22.7 10.9 23.7 2.26 311.64 37.9 1.9 0.3 32.4 673.4 -36.07 -144.3 96.0 840.73 1.2 2.64 Phoenix dactylifera 39.3 21.4 36.8 4.32 531.62 21.5 1.1 0.2 18.3 381.1 -253.34 -1,013.3 -110.3 -100.67 1.2 -0.32 Washingtonia robusta 16.0 8.7 14.9 1.76 215.83 9.4 0.5 0.1 8.0 167.0 -100.82 -403.3 -41.4 -20.46 1.2 -0.07

Other trees 210.0 96.7 207.6 19.79 2,783.08 334.9 17.1 3.0 286.1 5,945.8 -493.80 -1,975.2 681.4 6,753.73 15.5 1.70

CITYWIDE TOTAL 1,446 699 1,461 143 $19,590 2,181 111 20 1,864 $38,728 -5,030 -$20,120 2,894 $38,197 100% $1.48


Stormwater Runoff Reductions According to Federal Clean Water Act regulations, municipalities must obtain a permit for managing their stormwater discharges into water bodies. Each city’s program must identify the best management practices (BMPs) it will implement to reduce its pollutant discharge.

Rainfall interception by trees can reduce the amount of stormwater that enters collection and treatment facilities during large storm events. Trees intercept rainfall in their canopy, acting as mini-reservoirs, controlling runoff at the source. This is especially important in an urban setting with a significant quantity of impervious surfaces near a major waterway. Healthy urban trees can reduce the amount of runoff and pollutant loading in receiving waters in three primary ways:

● Leaves and branch surfaces intercept and store rainfall, thereby reducing runoff volumes and delaying the onset of peak flows.

● Root growth and decomposition increase the capacity and rate of soil infiltration by rainfall and reduce overland flow.

● Tree canopies reduce soil erosion and surface flows by diminishing the impact of raindrops on barren surfaces.

Henderson’s inventoried public trees intercept 7.7 million gallons of stormwater annually for an average of 298 gallons per tree (Table 9). The total annual value of this benefit to the City is $36,857, an average of $1.43 per tree. Pinus halepensis (Aleppo pine) are currently providing the greatest per tree benefit of $6.24 and the third highest percentage of overall stormwater benefits of 9.5% (Figure 9). Owing to their prevalence in the overall population, Pinus eldarica (Mondale pine) have the greatest percentage of overall stormwater benefits (17.2%), though the per tree benefit is $2.49. Many of the species currently demonstrating very low benefits, including Chilopsis linearis (desert willow, $0.22/tree) and Vitex agnus-castus (chaste tree, $0.38/tree), are immature populations of small-growing trees and will most likely not increase as those species age.

Figure 9. Annual Reduction in Stormwater Runoff - Top 5 Species

$0 $2 $4 $6 $8

Pinus halepensis

Pinus eldarica


Quercus virginiana

Parkinsonia florida

$6.24

$2.49

$2.23 $2.17

$1.93


Table 9 Annual Stormwater Runoff Reduction Benefits Provided by Henderson’s Public Tree Resource

Species Total Rainfall Interception

(Gal) Total ($) % of

Pop. % of

Total $ Avg.

$/tree

Pinus eldarica 1,321,968 6,346 9.9 17.2 2.49 Fraxinus velutina 'Fan-Tex' 842,912 4,046 8.7 11.0 1.80 Chilopsis linearis 89,257 428 7.7 1.2 0.22 Parkinsonia x 'Desert Museum' 155,611 747 6.0 2.0 0.48

Acacia stenophylla 285,399 1,370 5.3 3.7 1.00 Quercus virginiana 532,853 2,558 4.6 6.9 2.17 Prosopis glandulosa 193,178 927 4.3 2.5 0.84 Ulmus parvifolia 402,492 1,932 4.2 5.2 1.81 Prosopis velutina 256,464 1,231 4.1 3.3 1.18 Vitex agnus-castus 74,502 358 3.6 1.0 0.38 Fraxinus velutina 237,875 1,142 3.6 3.1 1.25 Pistacia chinensis 218,428 1,049 3.4 2.8 1.21 Acacia farnesiana 125,730 604 3.4 1.6 0.70 Prosopis alba 130,845 628 3.3 1.7 0.75 Parkinsonia florida 250,055 1,200 2.4 3.3 1.93 Chiltalpa tashkentensis 137,544 660 2.3 1.8 1.12 Pinus halepensis 728,832 3,499 2.2 9.5 6.24 Fraxinus angustifolia 259,701 1,247 2.2 3.4 2.23 Prosopis chilensis 127,069 610 1.2 1.7 1.91 Phoenix dactylifera 69,915 336 1.2 0.9 1.07 Washingtonia robusta 46,307 222 1.2 0.6 0.74 Other trees 1,191,150 5,718 15.5 15.5 1.44

CITYWIDE TOTAL 7,678,088 $36,857 100% 100% $1.43


Urban trees promote retail shopping by stimulating more frequent visits and a willingness to pay more for goods and

services (Wolf 1999).

Trees provide beauty in the urban landscape.

Aesthetic, Property Value & Socioeconomic Benefits Trees provide beauty in the urban landscape, privacy to homeowners, improved human health, a sense of comfort and place, and habitat for urban wildlife. There is documented evidence that trees promote better business by stimulating more frequent and extended shopping and a

willingness to pay more for goods and parking (Wolf, 1999). Some of these benefits may be captured as a percentage of the value of the property on which a tree stands. To determine the value of these less tangible benefits, i-Tree Streets uses research that compares differences in sales prices of homes to estimate the contribution associated with trees.

Differences in housing prices in relation to the presence (or lack) of a street tree help define the aesthetic value of street trees in the urban

environment. Consideration is given to the location of the street tree in relation to the land use. Street trees located in front of multi-family homes will not

increase the property value at the same rate as single-family homes.

Furthermore, street trees located adjacent to commercial and nonresidential properties do not have the same resale potential as residential areas. These factors are taken into consideration and the value of those trees is adjusted accordingly. The calculation of annual aesthetic and other benefits corresponds with a tree’s annual increase in leaf area. When a tree is actively growing, leaf area may increase dramatically. Once a tree is mature, there may be little or no net increase in leaf area from one year to the next; thus, there is little or no incremental annual aesthetic benefit for that year, although the cumulative benefit over the course of the entire life of the tree may be large. Since this report represents a one-year sample snapshot of the public tree population, aesthetic benefits reflect the increase in leaf area for each species population over the course of a single year. As a result, a very young population of 100 Fraxinus velutina ‘Fan-Tex’ (Fan-Tex ash) will have a greater annual aesthetic benefit than an equal number of mature Quercus virginiana (southern live oak). However, the cumulative lifetime aesthetic value of Quercus virginiana would be greater than that of Fraxinus velutina ‘Fan-Tex’.

The total annual benefit associated with property value increases and other less tangible benefits is $691,883, an average of $27.87 per tree (Table 11). Tree species that produced the highest average per tree aesthetic benefits are Pinus halepensis (Aleppo pine, $76.60), followed by Fraxinus angustifolia (Raywood ash, $45.99).

As a population, Fraxinus velutina ‘Fan-Tex’ contribute 13.9% of the overall benefits while representing on 8.7% of the population.


Figure 10. Annual Increase in Property and Socioeconomic Values - Top 5 Species

Table 10. Annual Property Value, Aesthetic,

and Socioeconomic Benefits of Henderson’s Tree Resource

Species Total ($) % of Pop.

% of Total $

Avg. $/tree

Pinus eldarica 55,635 9.9 8.0 21.85 Fraxinus velutina 'Fan-Tex' 95,889 8.7 13.9 42.58 Chilopsis linearis 18,211 7.7 2.6 9.17 Parkinsonia x 'Desert Museum' 17,369 6.0 2.5 11.24

Acacia stenophylla 25,932 5.3 3.8 19.00 Quercus virginiana 44,989 4.6 6.5 38.16 Prosopis glandulosa 35,530 4.3 5.1 32.21 Ulmus parvifolia 48,505 4.2 7.0 45.42 Prosopis velutina 37,431 4.1 5.4 35.82 Vitex agnus-castus 9,903 3.6 1.4 10.60 Fraxinus velutina 26,595 3.6 3.8 29.13 Pistacia chinensis 22,444 3.4 3.2 25.80 Acacia farnesiana 10,641 3.4 1.5 12.34 Prosopis alba 10,761 3.3 1.6 12.87 Parkinsonia florida 21,517 2.4 3.1 34.65 Chiltalpa tashkentensis 8,913 2.3 1.3 15.08 Pinus halepensis 42,973 2.2 6.2 76.60 Fraxinus angustifolia 25,752 2.2 3.7 45.99 Prosopis chilensis 13,817 1.2 2.0 43.31 Phoenix dactylifera 1,196 1.2 0.2 3.82 Washingtonia robusta 2,469 1.2 0.4 8.17 Other trees 115,410 15.5 16.7 28.99

CITYWIDE TOTAL $691,883 100% 100% $26.87

$0 $20 $40 $60 $80

Pinus halepensis


Ulmus parvifolia

Prosopis chilensis


$76.60

$45.99

$45.42 $43.31

$42.58


Benefit Summary Henderson’s public trees have beneficial effects on the community. Annual increases in property value, socioeconomic, and other aesthetic values are substantial, accounting for almost 80% of the total benefits.

Approximately 20% ($177,906) of the total annual benefits quantified in this study are environmental services (Table 13). Energy savings ($87,518) account for nearly 50% of the annual environmental benefits and 10% of all annual benefits. Air quality benefits ($38,197) account for 21% of annual environmental benefits and 4% of all annual benefits. Stormwater benefits ($36,857) account for 21% of the annual environmental benefits and 4% of all benefits. Carbon reduction benefits, valued at $15,334, account for 9% of environmental benefits and 1.7% of all benefits.

Table 11. Summary of Average Current Annual Per Tree Related Benefits from Henderson’s Tree Resource

Species Energy CO2 Air Quality Stormwater Aesthetic/Other Total

Pinus eldarica 4.80 0.74 3.31 2.49 21.85 33.20 Fraxinus velutina 'Fan-Tex' 4.55 0.76 2.45 1.80 42.58 52.14

Chilopsis linearis 1.03 0.16 0.13 0.22 9.17 10.71 Parkinsonia x 'Desert Museum' 1.39 0.29 0.59 0.48 11.24 13.98

Acacia stenophylla 2.02 0.28 1.25 1.00 19.00 23.56 Quercus virginiana 4.78 1.33 -3.48 2.17 38.16 42.95 Prosopis glandulosa 2.07 0.36 1.04 0.84 32.21 36.52 Ulmus parvifolia 6.03 0.88 3.91 1.81 45.42 58.05 Prosopis velutina 2.92 0.50 1.53 1.18 35.82 41.94 Vitex agnus-castus 1.12 0.23 0.43 0.38 10.60 12.76 Fraxinus velutina 3.94 0.73 2.40 1.25 29.13 37.45 Pistacia chinensis 4.11 0.59 0.49 1.21 25.80 32.20 Acacia farnesiana 1.94 0.42 0.96 0.70 12.34 16.36 Prosopis alba 1.27 0.25 0.43 0.75 12.87 15.57 Parkinsonia florida 5.45 0.87 2.99 1.93 34.65 45.89 Chiltalpa tashkentensis 3.09 0.69 1.61 1.12 15.08 21.58 Pinus halepensis 9.22 1.74 4.14 6.24 76.60 97.94 Fraxinus angustifolia 5.50 0.91 3.12 2.23 45.99 57.74 Prosopis chilensis 4.78 0.79 2.64 1.91 43.31 53.43 Phoenix dactylifera 2.86 0.38 -0.32 1.07 3.82 7.81 Washingtonia robusta 1.26 0.26 -0.07 0.74 8.17 10.37 Other trees 3.38 0.59 1.70 1.44 28.99 36.09

Citywide average $3.40 $0.60 $1.48 $1.43 $26.87 $33.78


Figure 11. Summary of Annual per Tree Benefits from Henderson’s Most Prevalent Tree Species

Pinus halepensis

Ulmus parvifolia


Prosopis chilensis


Parkinsonia florida

Quercus virginiana

Prosopis velutina

Fraxinus velutina

Prosopis glandulosa

Pinus eldarica

Pistacia chinensis

Acacia stenophylla

Chiltalpa tashkentensis

Acacia farnesiana

Prosopis alba


Vitex agnus-castus

Chilopsis linearis

Washingtonia robusta

Phoenix dactylifera

Other trees

$97.94

$58.05

$57.74

$53.43

$52.14

$45.89

$42.95

$41.94

$37.45

$36.52

$33.20

$32.20

$23.56

$21.58

$16.36

$15.57

$13.98

$12.76

$10.71

$10.37

$7.81

$36.09

Energy

CO2

Air Quality

Stormwater

Aesthetic/Other


Net Benefits and Benefit-Investment Ratio (BIR) Henderson receives substantial benefits from public trees; however, the City must also consider the costs of maintaining this resource. Applying a benefit-investment ratio (BIR) is a useful way to evaluate the public investment in the community tree population. A BIR is an indicator used to summarize the overall value compared to the costs of a given project. Specifically, in this analysis, BIR is the ratio of the total benefits provided by the City’s public trees expressed in monetary terms compared to the costs (investment) associated with their management, also expressed in monetary terms.

The estimated sum of benefits provided by Henderson’s public tree resource is $869,789, a value of $33.78 per tree and $3.24 per capita. These benefits are realized on an annual basis. It is important to acknowledge that this is not a full accounting of the benefits provided by this public tree resource, as some benefits are intangible and/or difficult to quantify, such as impacts on psychological health, crime, and violence. Empirical evidence of these benefits does exist (Wolf, 2007; Kaplan, 1989; Ulrich, 1986), but there is limited knowledge about the physical processes at work and their interactions make quantification imprecise. Tree growth and mortality rates are highly variable. A true and full accounting of benefits and costs must consider variability among sites (e.g., tree species, growing conditions, maintenance practices) throughout the City, as well as variability in tree growth. In other words, trees are worth far more than what one can ever quantify!

The total annual quantifiable benefit that public trees provide to the City of Henderson is $869,789. When the City’s annual tree related expenditures (or investment) of $304,139 are considered, the net annual benefit (benefits minus investment) to the City is $565,650. The average net benefit for an individual public tree in Henderson is $21.97 and the per capita net benefit is $2.11. Based on the inventory of 25,753 public trees, Henderson is receiving $2.86 in benefits for every $1 that is spent on its urban forest resource (Table 13). Considering the relatively young age of this tree population (56% are <7" DBH and 28% are between 7" and 25" DBH), Henderson can expect greater benefits as these tress continue to mature.


Total Annual Benefits from Henderson's Public Tree Resource: $869,789

Average Annual per Tree Benefits: $33.78 Annual Value of Benefits Per Capita: $3.24

Total Annual Investment to Maintain Henderson’s Public Tree Resource: $304,139 Average Annual per Tree Investment: $13.82 Annual Investment Per Capita: $1.13

Annual Net Benefits of Henderson’s Public Tree Resource: $565,650 For EVERY $1 Invested in public trees, Henderson receives $2.86 in Benefits.

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$15,334 - Carbon

$36,857 - Stormwater

$38197 - Air Quality

$87,518 - Energy

$691,883 - Aesthetic/Other

$0

$100,000

$200,000

$300,000

$400,000

$500,000

$600,000

$700,000

$800,000

$900,000

Annual Benefits $869,789

Net Benefit $565,650

Annual Investment $304,139

$0

$100,000

$200,000

$300,000

$400,000 $5,500 - Planting

$10,000 - Litter Clean-up

$15,000 - Infrastructure Repairs

$25,000 - Contract Pruning

$78,639 - Administration

$170,000 - Irrigation


Table 12. Benefit Versus Investment Summary for Henderson’s Public Tree Resource

Benefits Total ($) $/tree $/capita Energy 87,518 3.40 0.33 CO2 15,334 0.60 0.06 Air Quality 38,197 1.48 0.14 Stormwater 36,857 1.43 0.14 Aesthetic/Other 691,883 26.87 2.58

Total Benefits $869,789 $33.78 $3.24

Investment Planting 5,500 0.21 0.02 Contract Pruning 25,000 0.97 0.09 Pest Management 0 0.00 0.00 Irrigation 170,000 6.60 0.63 Removal 0 0.00 0.00 Administration 78,639 3.05 0.29 Inspection/Service 0 0.00 0.00 Infrastructure Repairs 15,000 0.58 0.06 Litter Clean-up 10,000 0.39 0.04 Liability/Claims 0 0.00 0.00 Other Costs 0 0.00 0.00

Total Investment $304,139 $11.81 $1.13

Net Benefits $565,650 $21.97 $2.11

Benefit-cost ratio 2.86


Conclusion This analysis describes the current structural characteristics of Henderson’s inventoried municipal forest using established tree sampling, numerical modeling, and statistical methods to provide a general accounting of the benefits produced by this public tree resource. The analysis provides a “snapshot” of this resource at its current population and condition level. Rather than examining each individual tree as an inventory does, the resource analysis examines trends and performance measures over the entire urban forest and each of the major species populations within.

When evaluating the bottom line, Henderson’s public trees are worth the investment. This public resource gives back more in quantifiable benefits, including energy savings, stormwater runoff reduction, reduction in atmospheric CO2, and aesthetic benefits, than the community invests in its care. The City’s 25,753 trees are providing $869,789 in annual gross benefits, a value of $33.78 per tree and $3.24 per capita. Taking into consideration the investment necessary to manage this resource, ($304,139), Henderson’s public trees provide $565,650 in net benefits. That is an average of $21.97 per tree and $2.11 per capita. For every $1 invested in Henderson’s public trees, the community receives $2.86 in benefits.

Henderson’s inventoried urban forest is quite young and in good condition with 127 different species. Although it is critical to maintain an adequate level of resources to protect and nurture this resource, Henderson’s public trees can be expected to provide even greater benefits in the future and for many generations to come. The City can focus resources on maximizing the flow of benefits from the current tree population and maintaining a forward-thinking approach. Based on the resource analysis, Davey Resource Group recommends the following:

● Work toward developing an appropriate age distribution. Henderson’s tree population is very heavily weighted toward small, young trees. This is likely indicative of the rapid growth Henderson has experienced in terms of human population over the last two decades. Henderson should work to offset this by implementing a nutrition-fertilization program to help maximize healthy tree growth.

● Maximize the benefits of the existing tree resource through comprehensive tree maintenance and a cyclical pruning schedule.

● Implement a structural pruning program for young and establishing trees to promote healthy structure, extend life expectancy, and reduce future costs and liability. This is especially important in the case of Henderson with such a large population of young trees.

● Continue to develop species diversity. While Henderson does not have any species comprising greater than 10% of the overall population, there are under-represented species and genera that Henderson could focus planting to improve overall diversity among its tree population.

● Maintain the inventory in an existing or newly purchased asset management system.

● Inventory the remainder of the urban forest, and update with new trees as they are planted.

Understanding the current status of the City’s tree population allows forest managers to consider what future trends are likely and what management challenges will need to be met to sustain or, more importantly, increase the current level of benefits. Performance data from the analysis can be used to make determinations regarding species selection, distribution, and maintenance policies. Documenting current structure is necessary for establishing goals and performance


objectives and can serve as a benchmark for measuring future success. Information from the urban forest resource analysis can be used to create an urban forest management or master plan. An urban forest master plan is a critical tool for successful urban forest management, inspiring commitment and providing vision for communication with key decision-makers both inside and outside the organization.

As a Tree City, USA with a forward-looking approach to urban forest management, Henderson, Nevada is a community that recognizes the vital importance of trees to the environmental, social, and economic well-being of the City. Henderson has demonstrated that public trees are a valued community resource, a vital component of the urban infrastructure, and an important part of the City’s history and identity. The City takes a proactive and forwarding-looking approach to caring for the community’s trees, as evidenced by the condition and structure of this public resource. Current and complete inventory data will help staff to more efficiently track maintenance activities and tree health and will provide a strong basis for making informed management decisions. With additional tree planting and continued proactive management, Henderson’s urban forest can be expected to produce an even greater flow of benefits as this resource continues to mature. With a demonstrated commitment to maintaining and maximizing the benefits from its public trees, the community will always be able to enjoy the richness of life afforded by the City of Henderson.


Appendix A: Methods and Procedures Henderson’s tree inventory was collected by Certified Arborists, using ArcPad software to assist the inventory arborist in locating the sample plots on the ground and inputting tree attributes (details about each tree’s species, size, and condition). The data was formatted for use in i-Tree’s public tree population assessment tool, i-Tree Streets, a STRATUM Analysis Tool (Streets v 5.0.1; i-Tree v 5.0.6). i-Tree Streets assesses tree population structure and the function of those trees, such as their role in building energy use, air pollution removal, stormwater interception, carbon dioxide removal, and property value increases. In order to analyze the economic benefits of Henderson’s trees, i-Tree Streets calculates the dollar value of annual resource functionality and compares that to annual program expenditures. This analysis combines the results of the City’s tree inventory with benefit-cost modeling data to produce information regarding resource structure, function, and value for use in determining management recommendations. i-Tree Streets regionalizes the calculations of its output by incorporating detailed reference City project information for 17 climate zones across the United States (Henderson is located in the Southwest Desert Climate Zone).

For each of the modeled benefits, an annual resource unit was determined on a per tree basis. Resource units are measured as MWh of electricity saved per tree; MBtu of natural gas conserved per tree, pounds of atmospheric CO2 reduced per tree; pounds of NO2, PM10, and VOCs reduced per tree; cubic feet of stormwater runoff reduced per tree; and square feet of leaf area added per tree to increase property values.

Prices were assigned to each resource unit using economic indicators of society’s willingness to pay for the environmental benefits trees provide. Estimates of benefits are initial approximations as some benefits are difficult to quantify (e.g., impacts on psychological health, crime, and violence). In addition, limited knowledge about the physical processes at work and their interactions makes estimates imprecise (e.g., fate of air pollutants trapped by trees and then washed to the ground by rainfall). Therefore, this method of quantification provides first-order approximations based on current research. It is intended to be a general accounting of the benefits produced by urban trees.

Table 13. Henderson Benefit Prices Used In This Analysis

Benefits Price Unit Source Electricity $0.0671 $/Kwh Submitted by City of Henderson Natural Gas $0.6455 $/Therm Submitted by City of Henderson CO2 $0.0075 $/lb Streets default – Southwest Desert PM10 $6 $/lb Streets default – Southwest Desert NO2 $4 $/lb Streets default – Southwest Desert SO2 $15.70 $/lb Streets default – Southwest Desert VOC $4 $/lb Streets default – Southwest Desert Stormwater Interception $0.0048 $/gallon Streets default – Southwest Desert Median Home Value $135,000 $ Submitted by City of Henderson

i-Tree Streets default values (Table 14) from the Southwest Desert Climate Zone were used for all benefit prices except for median home values and electric and natural gas rates. Electric rates, Natural Gas rates, and Median home value for Henderson was submitted by the City of Henderson. Using these rates, the magnitude of the benefits provided by the public tree resource was calculated using i-Tree Streets. Program budget values used in benefit versus investment ratio calculations were supplied by City of Henderson.


Appendix B: References Akbari, H., D. Kurn, et al. 1997. Peak power and cooling energy savings of shade trees. Energy and Buildings 25:139–148.

Bell ML, McDermott A, Zeger SL, Samet JM, Dominici F. 2004. Ozone and short-term mortality in 95 US urban communities, 1987-2000. J Amer Med Assoc 292:2372-2378.

Chandler TJ. 1965. The Climate of London. London:Hutchinson.

Clark County Department of Air Quality, Nevada. Air Quality Current Rules and Regulations. http://www.clarkcountynv.gov/Depts/AirQuality/Pages/Rules_CurrentRulesandRegulations.aspx

Clark County Department of Air Quality, Nevada. Air Quality In Clark County. http://ccaqapps5m.co.clark.nv.us/

Clark JR, Matheny NP, Cross G, Wake V. 1997. A model of urban forest sustainability. J Arbor 23(1):17-30.

CTLA. 1992. Guide for Plant Appraisal. 8th ed. Savoy, IL: ISA. 103 p.

CUFR. Center For Urban Forest Research Pacific Southwest Research Station. http://www.fs.fed.us/psw/programs/cufr/

Cullen S. 2002. Tree appraisal: can depreciation factors be rated greater than 100%? J Arbor 28(3):153-158.

EPA, US Environmental Protection Agency. Heat Island Effect. www.epa.gov/heatisland/about/index.htm

EPA, US Environmental Protection Agency. National Ambient Air Quality Standards (NAAQS). http://www.epa.gov/air/criteria.html

Huang, J., H. Akbari, and H. Taha. 1990. The Wind-Shielding and Shading Effects of Trees on Residential Heating and Cooling Requirements. ASHRAE Winter Meeting, American Society of Heating, Refrigerating and Air-Conditioning Engineers. Atlanta, Georgia.

Heisler GM. 1986. Energy savings with trees. J Arbor 12(5):113–125.

i-Tree, STRATUM, http://www.itreetools.org/

Kaplan, Rachel and Stephen. 1989. The Experience of Nature: A Psychological Perspective. Cambridge: Cambridge University Press.

Kurn, D., S. Bretz, B. Huang, and H. Akbari. 1994. The Potential for Reducing Urban Air Temperatures and Energy Consumption through Vegetative Cooling (PDF) (31 pp, 1.76MB). ACEEE Summer Study on Energy Efficiency in Buildings, American Council for an Energy Efficient Economy. Pacific Grove, California.

Maco SE, McPherson EG. 2002. Assessing canopy cover over streets and sidewalks in street tree populations. J Arbor 28(6):270-276.

Maco SE, McPherson EG. 2003. A practical approach to assessing structure, function, and value of street tree populations in small communities. J Arbor 29(2):84-97.

http://www.clarkcountynv.gov/Depts/AirQuality/Pages/Rules_CurrentRulesandRegulations.aspx

http://www.clarkcountynv.gov/Depts/AirQuality/Pages/Rules_CurrentRulesandRegulations.aspx

http://www.epa.gov/heatisland/about/index.htm


McPherson EG, Rowntree RA. 1989. Using structural measures to compare twenty two US street tree populations. Land J 8:13-23.

McPherson EG. 1993. Evaluating the cost-effectiveness of shade trees for demand-side management. Elec J 6(9):57-65.

McPherson, E.G., J. R. Simpson, P. J. Peper, S. E. Maco, and Q. Xiao. 2005. Municipal forest benefits and costs in five US cities (PDF) (6 pp, 267K). Journal of Forestry 103(8):411–416.

McPherson et al. 2008. Urban Forest Greenhouse Gas Reporting Protocol

Miller RW. 1997. Urban forestry: planning and managing urban greenspaces. 2nd ed.

Moll G, Kollin C. 1993. A new way to see our City forests. American Forests 99(9-10): 29-31.

Richards NA. 1982/83. Diversity and stability in a street tree population. Urban Ecology. 7:159–171.

Ulrich, Roger S. 1986. Human Responses to Vegetation and Landscapes. Landscape and Urban Planning, 13, 29-44.

Watson G. 2002. Comparing formula methods of tree appraisal. Journal of Arboriculture. 28(1): 11-18.

Williams E, Lotstein R, Galik C, Knuffman H. 2007. A Convenient Guide to Climate Change Policy and Technology. Vol2: 134 p

Wolf, K.L. 2007. The Environmental Psychology of Trees. International Council of Shopping Centers Research Review. 14, 3:39-43.


Appendix C: Reports Henderson Complete Population of Public Trees

DBH Class (in)

Species 0-4 4-7 7-13 13-19

19-25

25-31

31-37

37-42 > 42 Total % of

Pop.

Broadleaf Deciduous Large (BDL) Gleditsia triacanthos 68 72 98 0 0 0 0 0 0 238 0.9 Populus fremontii 107 19 19 3 0 0 1 0 0 149 0.6 Platanus wrightii 57 0 22 11 6 1 0 0 0 97 0.4 Fraxinus uhdei 7 26 35 14 0 0 0 0 0 82 0.3 Quercus muehlenbergii 13 16 2 0 0 0 0 0 0 31 0.1 Quecus shumardii 14 6 6 1 0 0 0 0 0 27 0.1 Plantanus occidentalis 10 5 6 6 0 0 0 0 0 27 0.1 Populus spp. 5 21 0 0 0 0 0 0 0 26 0.1 Ulmus pumila 6 3 8 0 0 0 0 0 0 17 0.1 Quercus buckleyi (texana) 8 1 1 0 0 0 0 0 0 10 0.0 Quercus lobata 1 0 5 3 0 0 0 0 0 9 0.0 Sophora japonica 1 2 5 0 0 0 0 0 0 8 0.0 Celtis sinensis 0 2 0 0 0 0 0 0 0 2 0.0 Zelkova serratta 1 1 0 0 0 0 0 0 0 2 0.0 Fraxinus americana junginger 1 0 0 0 0 0 0 0 0 1 0.0 Carya illinoinensis 1 0 0 0 0 0 0 0 0 1 0.0

Total 300 174 207 38 6 1 1 0 0 727 2.8

Broadleaf Deciduous Medium (BDM) Fraxinus velutina 'Fan-Tex' 778 873 517 83 1 0 0 0 0 2,252 8.7 Ulmus parvifolia 578 288 155 46 1 0 0 0 0 1,068 4.1 Fraxinus velutina 369 214 258 68 3 1 0 0 0 913 3.5 Pistacia chinensis 351 221 272 26 0 0 0 0 0 870 3.4 Parkinsonia florida 221 222 149 27 2 0 0 0 0 621 2.4 Fraxinus angustifolia 181 171 159 47 2 0 0 0 0 560 2.2 Prosopis chilensis 116 107 79 16 1 0 0 0 0 319 1.2 Robinia pseudoacacia 44 111 55 5 0 0 0 0 0 215 0.8 Parkinsonia aculeata 27 34 35 8 0 0 0 0 0 105 0.4 Morus alba 2 1 1 20 22 12 6 0 0 64 0.2 Koelreuteria paniculata 21 7 10 0 0 0 0 0 0 38 0.1 Celtis reticulata 21 0 0 0 0 0 0 0 0 21 0.1 Robinia ambigua 'Purple Rose' 19 2 0 0 0 0 0 0 0 21 0.1

Fraxinus velutina 'Glabra' 4 3 7 4 0 0 0 0 0 18 0.1 Melia azedarach 6 5 3 0 0 0 0 0 0 14 0.1 Celtis occidentalis 7 2 1 0 0 0 0 0 0 10 0.0 Salix gooddingii 7 0 1 1 0 0 0 0 0 9 0.0 Albizia julibrissin 5 0 3 0 0 0 0 0 0 8 0.0 Pistacia vera 2 0 3 0 0 0 0 0 0 5 0.0


Machaerium tipu 0 0 0 1 0 0 1 0 0 2 0.0

Total 2,759 2,261 1,708 352 32 13 7 0 0 7,133 27.7

Broadleaf Deciduous Small (BDS) Chilopsis linearis 1,570 334 75 5 0 0 0 0 0 1,984 7.7 Parkinsonia x 'Desert Museum' 1,243 252 50 1 0 0 0 0 0 1,546 6.0

Prosopis glandulosa 846 156 89 12 0 0 0 0 0 1,103 4.3 Prosopis velutina 642 254 127 18 4 0 0 0 0 1,045 4.1 Vitex agnus-castus 852 75 7 0 0 0 0 0 0 934 3.6 Acacia farnesiana 576 185 78 21 2 0 0 0 0 863 3.4 Chiltalpa tashkentensis 148 289 145 9 0 0 0 0 0 591 2.3 Prosopis torreyana 91 59 33 6 1 0 0 0 0 190 0.7 Prosopis species 49 98 31 7 0 0 0 0 0 185 0.7 Prosopis pubescens 112 52 19 2 0 0 0 0 0 185 0.7 Cercis canadensis 59 6 4 0 0 0 0 0 0 69 0.3 Parkinsonia microphylla 43 13 1 0 0 0 0 0 0 57 0.2 Prunus cerasifera 17 17 3 0 0 0 0 0 0 37 0.1 Cercidium praecox 5 20 7 0 0 0 0 0 0 32 0.1 Parkinsonia x 'Sonoran Emerald' 13 8 1 0 0 0 0 0 0 22 0.1

Pyrus calleryana 2 10 8 0 0 0 0 0 0 20 0.1 Prosopis juliflora 7 5 3 0 0 0 0 0 0 16 0.1 Lagerstroemia indica 6 8 0 0 0 0 0 0 0 14 0.1 Quercus gambelli 0 0 2 1 0 0 0 0 0 3 0.0 Tamarix chinensis 2 0 0 0 0 0 0 0 0 2 0.0 Cercis canadensis texensis 2 0 0 0 0 0 0 0 0 2 0.0 Ficus carica 2 0 0 0 0 0 0 0 0 2 0.0 Prunus armeniaca 1 0 0 0 0 0 0 0 0 1 0.0 Cercis reniformis 1 0 0 0 0 0 0 0 0 1 0.0 Malus spp. 1 0 0 0 0 0 0 0 0 1 0.0 Cercis orbiculata 1 0 0 0 0 0 0 0 0 1 0.0 Punica granatum 1 0 0 0 0 0 0 0 0 1 0.0 Prunus spp. 0 1 0 0 0 0 0 0 0 1 0.0

Total 6,292 1,842 683 82 7 0 0 0 0 8,908 34.6

Broadleaf Evergreen Large (BEL) Quercus ilex 66 11 0 0 0 0 0 0 0 77 0.3 Eucalyptus microtheca 69 1 1 3 0 0 0 0 0 74 0.3 Eucalyptus camaldulensis 6 2 5 0 2 0 0 0 0 15 0.1 Eucalyptus papuana 7 1 0 0 0 0 0 0 0 8 0.0 Quercus suber 1 1 1 0 0 0 0 0 0 3 0.0 Eucalyptus microcarpa 0 2 0 0 0 0 0 0 0 2 0.0 Eucalyptus spp. 0 0 1 0 0 0 0 0 0 1 0.0

Total 149 18 8 3 2 0 0 0 0 180 0.7

Broadleaf Evergreen Medium (BEM) Quercus virginiana 261 387 476 54 1 0 0 0 0 1,179 4.6


Prosopis alba 545 122 139 28 2 0 0 0 0 836 3.2 Brachychiton populneum 12 22 6 0 0 0 0 0 0 40 0.2 Acacia salicina 0 17 1 0 0 0 0 0 0 18 0.1 Quercus fusiformis 12 2 0 0 0 0 0 0 0 14 0.1 Schinus molle 1 0 2 0 0 0 0 0 0 3 0.0 Laurus nobillis 1 0 0 0 0 0 0 0 0 1 0.0

Total 832 550 624 82 3 0 0 0 0 2,091 8.1

Broadleaf Evergreen Small (BES) Acacia stenophylla 721 471 153 19 1 0 0 0 0 1,365 5.3 Sophora secundiflora 182 5 0 0 0 0 0 0 0 187 0.7 Acacia aneura 146 35 2 0 0 0 0 0 0 183 0.7 Olea europaea 38 80 47 2 0 0 0 0 0 167 0.6 Acacia greggii 143 17 2 1 0 0 0 0 0 163 0.6 Rhus lancea 56 32 27 0 0 0 0 0 0 115 0.4 Olea europaea 'Swan Hill' 86 9 10 0 0 0 0 0 0 105 0.4 Pyrus kawakamii 0 56 33 6 0 0 0 0 0 95 0.4 Chamaerops humilis 2 47 10 5 0 0 0 0 0 64 0.2 Yucca brevifolia 0 16 21 2 0 0 0 0 0 39 0.2 Acacia constricta 16 20 3 0 0 0 0 0 0 39 0.2 Ligustrum lucidum 7 16 10 0 0 0 0 0 0 33 0.1 Acacia schaffneri 19 2 2 0 0 0 0 0 0 23 0.1 Ebenopsis ebano 9 8 1 0 0 0 0 0 0 18 0.1 Olneya tesota 6 3 7 1 0 0 0 0 0 17 0.1 Arbutus unedo 1 10 0 0 0 0 0 0 0 11 0.0 Prunus caroliniana 3 7 0 0 0 0 0 0 0 10 0.0 Salix exigua 8 0 0 0 0 0 0 0 0 8 0.0 Vauquelinia californica 4 0 1 0 0 0 0 0 0 5 0.0 Callistemon viminalis 4 0 0 0 0 0 0 0 0 4 0.0 Eucalyptus woodwardii 4 0 0 0 0 0 0 0 0 4 0.0 Leucaena retusa 3 0 1 0 0 0 0 0 0 4 0.0 Eucalyptus sargentii 3 0 0 0 0 0 0 0 0 3 0.0 Eucalyptus gillii 2 0 0 0 0 0 0 0 0 2 0.0 Acacia pendula 0 1 1 0 0 0 0 0 0 2 0.0 Fraxinus greggii 2 0 0 0 0 0 0 0 0 2 0.0 Nicotiana glauca 0 1 0 0 0 0 0 0 0 1 0.0 Celtis pallida 1 0 0 0 0 0 0 0 0 1 0.0 Caesalpinia cascalaco 1 0 0 0 0 0 0 0 0 1 0.0 Xylosma congestum 1 0 0 0 0 0 0 0 0 1 0.0 Unknown spp. 0 1 0 0 0 0 0 0 0 1 0.0 Simmondsia chinensis 1 0 0 0 0 0 0 0 0 1 0.0 Rhus ovata 0 1 0 0 0 0 0 0 0 1 0.0

Total 1,469 838 331 36 1 0 0 0 0 2,675 10.4

Conifer Evergreen Large (CEL) Pinus eldarica 364 613 951 498 116 4 0 0 0 2,546 9.9 Pinus halepensis 2 13 158 311 66 10 1 0 0 561 2.2 Pinus roxburghii 2 8 50 71 8 0 0 0 0 139 0.5


Pinus pinea 0 2 10 2 0 0 0 0 0 14 0.1 Cupressus sempervirens 0 6 0 0 0 0 0 0 0 6 0.0

Total 368 642 1,169 882 190 14 1 0 0 3,266 12.7

Conifer Evergreen Medium (CEM) Pinus brutia 0 6 2 3 0 0 0 0 0 11 0.0 Cupressus glabra 3 2 3 1 0 0 0 0 0 9 0.0

Total 3 8 5 4 0 0 0 0 0 20 0.1

Conifer Evergreen Small (CES) Fouquieria splendens 0 0 0 0 0 0 0 1 0 1 0.0 Juniperus spp. 0 0 1 0 0 0 0 0 0 1 0.0

Total 0 0 1 0 0 0 0 1 0 2 0.0

Palm Evergreen Large (PEL)

Phoenix canariensis 1 0 0 9 5 2 11 0 0 28 0.1 Trachycarpus fortunei 0 0 2 0 0 0 0 0 0 2 0.0

Total 1 0 2 9 5 2 11 0 0 30 0.1

Palm Evergreen Medium (PEM) Phoenix dactylifera 0 0 2 177 130 3 1 0 0 313 1.2

Total 0 0 2 177 130 3 1 0 0 313 1.2

Palm Evergreen Small (PES) Washingtonia robusta 0 5 46 236 15 0 0 0 0 302 1.2 Washingtonia filifera 0 1 10 28 21 24 2 3 0 89 0.3 Brahea armata 0 2 5 3 0 0 0 0 0 10 0.0 Butia capitata 0 0 0 4 0 0 0 0 0 4 0.0 Arecastrum romanzoffianum 0 0 3 0 0 0 0 0 0 3 0.0

Total 0 8 64 271 36 24 2 3 0 408 1.6

Grand Total 12,173 6,341 4,804 1,936 412 57 23 4 0 25,753 100%


Relative Performance Index (RPI) for Henderson’s Public Tree Species

Species Dead or Dying Poor Fair Good RPI # of Trees % of

Pop. Pinus eldarica 0.7 1.2 16.0 82.2 1.04 2,546 9.9 Fraxinus velutina 'Fan-Tex' 0.3 2.0 22.6 75.2 1.01 2,252 8.7 Chilopsis linearis 0.3 1.8 19.2 78.7 1.03 1,985 7.7 Parkinsonia x 'Desert Museum' 0.3 1.9 30.3 67.5 0.99 1,546 6.0 Acacia stenophylla 0.1 1.1 14.1 84.7 1.05 1,365 5.3 Quercus virginiana 1.1 5.2 25.0 68.7 0.98 1,179 4.6 Prosopis glandulosa 0.0 2.1 11.4 86.5 1.05 1,103 4.3 Ulmus parvifolia 0.4 4.3 44.1 51.2 0.93 1,068 4.1 Prosopis velutina 2.6 5.6 21.9 69.9 0.97 1,045 4.1 Vitex agnus-castus 0.5 1.3 16.1 82.1 1.04 934 3.6 Fraxinus velutina 2.1 3.7 39.1 55.1 0.93 913 3.5 Pistacia chinensis 0.2 0.9 14.3 84.6 1.05 870 3.4 Acacia farnesiana 0.3 1.6 28.6 69.4 0.99 863 3.4 Prosopis alba 0.8 2.3 30.6 66.3 0.98 836 3.2 Parkinsonia florida 3.2 2.7 29.0 65.1 0.96 621 2.4 Chiltalpa tashkentensis 0.2 6.4 51.1 42.3 0.89 591 2.3 Pinus halepensis 0.0 1.2 17.8 80.9 1.04 561 2.2 Fraxinus angustifolia 0.7 4.8 19.3 75.2 1.00 560 2.2 Prosopis chilensis 0.0 2.5 22.9 74.6 1.01 319 1.2 Phoenix dactylifera 0.0 0.0 2.6 97.4 1.09 313 1.2 Washingtonia robusta 0.7 6.0 1.7 91.7 1.05 302 1.2 Gleditsia triacanthos 4.6 7.6 24.4 63.4 0.93 238 0.9 Robinia pseudoacacia 2.8 6.5 33.0 57.7 0.93 215 0.8 Prosopis torreyana 0.0 2.1 13.7 84.2 1.04 190 0.7 Sophora secundiflora 0.0 2.7 7.5 89.8 1.06 187 0.7 Prosopis pubescens 1.1 4.9 5.9 88.1 1.04 185 0.7 Prosopis species 2.7 7.6 41.6 48.1 0.89 185 0.7 Acacia aneura 1.1 1.6 12.6 84.7 1.04 183 0.7 Olea europaea 0.0 2.4 31.1 66.5 0.99 167 0.6 Acacia greggii 0.6 3.7 36.2 59.5 0.95 163 0.6 Populus fremontii 4.0 10.1 11.4 74.5 0.96 149 0.6 Pinus roxburghii 0.0 0.7 18.0 81.3 1.04 139 0.5 Rhus lancea 0.9 7.0 40.0 52.2 0.92 115 0.4 Parkinsonia aculeata 4.8 18.1 39.0 38.1 0.81 105 0.4 Olea europaea 'Swan Hill' 0.0 0.0 6.7 93.3 1.08 105 0.4 Platanus wrightii 1.0 3.1 43.3 52.6 0.93 97 0.4 Pyrus kawakamii 1.1 9.5 25.3 64.2 0.95 95 0.4 Washingtonia filifera 0.0 0.0 4.5 95.5 1.09 89 0.3 Fraxinus uhdei 1.2 2.4 15.9 80.5 1.02 82 0.3 Quercus ilex 1.3 2.6 80.5 15.6 0.81 77 0.3 Eucalyptus microtheca 0.0 0.0 1.4 98.6 1.10 74 0.3 Cercis canadensis 7.2 13.0 69.6 10.1 0.72 69 0.3



Pop. Morus alba 0.0 1.6 21.9 76.6 1.02 64 0.2 Chamaerops humilis 0.0 0.0 0.0 100.0 1.10 64 0.2 Parkinsonia microphylla 3.5 7.0 63.2 26.3 0.82 57 0.2 Brachychiton populneum 0.0 2.5 7.5 90.0 1.06 40 0.2 Yucca brevifolia 0.0 0.0 7.7 92.3 1.08 39 0.2 Acacia constricta 0.0 0.0 12.8 87.2 1.06 39 0.2 Koelreuteria paniculata 2.6 5.3 7.9 84.2 1.02 38 0.1 Prunus cerasifera 2.7 10.8 35.1 51.4 0.89 37 0.1 Ligustrum lucidum 0.0 30.3 30.3 39.4 0.81 33 0.1 Cercidium praecox 0.0 3.1 6.3 90.6 1.06 32 0.1 Quercus muehlenbergii 3.2 0.0 9.7 87.1 1.04 31 0.1 Phoenix canariensis 0.0 0.0 3.6 96.4 1.09 28 0.1 Plantanus occidentalis 3.7 11.1 25.9 59.3 0.91 27 0.1 Quecus shumardii 3.7 3.7 25.9 66.7 0.96 27 0.1 Populus spp. 0.0 7.7 26.9 65.4 0.96 26 0.1 Acacia schaffneri 30.4 4.3 4.3 60.9 0.76 23 0.1 Parkinsonia x 'Sonoran Emerald' 0.0 0.0 4.5 95.5 1.09 22 0.1 Celtis reticulata 19.0 0.0 57.1 23.8 0.73 21 0.1 Robinia ambigua 'Purple Rose' 0.0 4.8 19.0 76.2 1.01 21 0.1 Pyrus calleryana 0.0 25.0 30.0 45.0 0.84 20 0.1 Ebenopsis ebano 0.0 0.0 33.3 66.7 0.99 18 0.1 Fraxinus velutina 'Glabra' 16.7 0.0 50.0 33.3 0.78 18 0.1 Acacia salicina 0.0 0.0 16.7 83.3 1.05 18 0.1 Ulmus pumila 0.0 0.0 23.5 76.5 1.03 17 0.1 Olneya tesota 0.0 0.0 5.9 94.1 1.08 17 0.1 Prosopis juliflora 0.0 0.0 12.5 87.5 1.06 16 0.1 Eucalyptus camaldulensis 0.0 0.0 33.3 66.7 0.99 15 0.1 Pinus pinea 0.0 0.0 14.3 85.7 1.06 14 0.1 Lagerstroemia indica 0.0 0.0 14.3 85.7 1.06 14 0.1 Quercus fusiformis 0.0 0.0 7.1 92.9 1.08 14 0.1 Melia azedarach 0.0 7.1 35.7 57.1 0.94 14 0.1 Arbutus unedo 0.0 9.1 9.1 81.8 1.01 11 0.0 Pinus brutia 0.0 9.1 36.4 54.5 0.92 11 0.0 Brahea armata 0.0 0.0 0.0 100.0 1.10 10 0.0 Prunus caroliniana 0.0 20.0 30.0 50.0 0.87 10 0.0 Celtis occidentalis 0.0 60.0 20.0 20.0 0.65 10 0.0 Quercus buckleyi (texana) 0.0 0.0 20.0 80.0 1.04 10 0.0 Cupressus glabra 0.0 11.1 22.2 66.7 0.96 9 0.0 Quercus lobata 0.0 0.0 55.6 44.4 0.92 9 0.0 Salix gooddingii 0.0 11.1 11.1 77.8 0.99 9 0.0 Albizia julibrissin 0.0 0.0 37.5 62.5 0.98 8 0.0 Sophora japonica 12.5 12.5 25.0 50.0 0.82 8 0.0 Eucalyptus papuana 25.0 0.0 25.0 50.0 0.78 8 0.0 Salix exigua 0.0 0.0 0.0 100.0 1.10 8 0.0



Pop. Cupressus sempervirens 16.7 0.0 0.0 83.3 0.94 6 0.0 Vauquelinia californica 0.0 0.0 20.0 80.0 1.04 5 0.0 Pistacia vera 0.0 0.0 40.0 60.0 0.97 5 0.0 Leucaena retusa 0.0 0.0 50.0 50.0 0.94 4 0.0 Callistemon viminalis 0.0 0.0 0.0 100.0 1.10 4 0.0 Eucalyptus woodwardii 0.0 25.0 25.0 50.0 0.86 4 0.0 Butia capitata 0.0 0.0 0.0 100.0 1.10 4 0.0 Quercus suber 0.0 0.0 33.3 66.7 0.99 3 0.0 Quercus gambelli 0.0 0.0 66.7 33.3 0.89 3 0.0 Schinus molle 0.0 0.0 0.0 100.0 1.10 3 0.0 Eucalyptus sargentii 0.0 0.0 33.3 66.7 0.99 3 0.0 Arecastrum romanzoffianum 0.0 100.0 0.0 0.0 0.45 3 0.0 Eucalyptus microcarpa 0.0 0.0 0.0 100.0 1.10 2 0.0 Machaerium tipu 0.0 0.0 50.0 50.0 0.94 2 0.0 Zelkova serratta 0.0 0.0 100.0 0.0 0.78 2 0.0 Tamarix chinensis 0.0 0.0 0.0 100.0 1.10 2 0.0 Cercis canadensis texensis 0.0 0.0 0.0 100.0 1.10 2 0.0 Celtis sinensis 50.0 50.0 0.0 0.0 0.29 2 0.0 Fraxinus greggii 0.0 0.0 0.0 100.0 1.10 2 0.0 Ficus carica 0.0 0.0 0.0 100.0 1.10 2 0.0 Acacia pendula 0.0 0.0 0.0 100.0 1.10 2 0.0 Eucalyptus gillii 50.0 0.0 0.0 50.0 0.62 2 0.0 Trachycarpus fortunei 0.0 0.0 50.0 50.0 0.94 2 0.0 Fraxinus americana junginger 0.0 0.0 0.0 100.0 1.10 1 0.0 Juniperus spp. 0.0 0.0 0.0 100.0 1.10 1 0.0 Prunus spp. 0.0 0.0 100.0 0.0 0.78 1 0.0 Fouquieria splendens 0.0 0.0 0.0 100.0 1.10 1 0.0 Caesalpinia cascalaco 0.0 0.0 100.0 0.0 0.78 1 0.0 Celtis pallida 0.0 0.0 0.0 100.0 1.10 1 0.0 Carya illinoinensis 0.0 0.0 0.0 100.0 1.10 1 0.0 Cercis reniformis 0.0 0.0 0.0 100.0 1.10 1 0.0 Laurus nobillis 0.0 0.0 0.0 100.0 1.10 1 0.0 Malus spp. 0.0 0.0 0.0 100.0 1.10 1 0.0 Eucalyptus spp. 0.0 0.0 0.0 100.0 1.10 1 0.0 Cercis orbiculata 0.0 100.0 0.0 0.0 0.45 1 0.0 Punica granatum 0.0 0.0 0.0 100.0 1.10 1 0.0 Nicotiana glauca 0.0 0.0 0.0 100.0 1.10 1 0.0 Xylosma congestum 0.0 0.0 100.0 0.0 0.78 1 0.0 Rhus ovata 0.0 0.0 0.0 100.0 1.10 1 0.0 Simmondsia chinensis 0.0 0.0 100.0 0.0 0.78 1 0.0 Prunus armeniaca 0.0 0.0 0.0 100.0 1.10 1 0.0

Citywide 0.8 2.9 23.0 73.2 1.00 25,753 100%


Replacement Value of Henderson’s Public Tree Species

DBH Class (in)

Species 0-4 4-7 7-13 13-19 19-25 25-31 31-37 37-42 > 42 Total % of Total

$ Pinus eldarica 100,287 756,601 3,696,338 4,933,176 2,097,624 117,204 0 0 0 11,701,229 19.7 Pinus halepensis 709 19,839 838,567 4,211,412 1,727,949 385,521 62,523 0 0 7,246,521 12.2 Fraxinus velutina 'Fan-Tex'

213,637 1,070,878 2,006,424 782,280 13,659 0 0 0 0 4,086,877 6.9

Quercus virginiana 77,504 618,521 2,488,597 745,674 27,024 0 0 0 0 3,957,320 6.7

Pistacia chinensis 135,618 486,740 1,869,800 473,274 0 0 0 0 0 2,965,432 5.0

Acacia stenophylla 244,772 810,296 818,490 251,654 27,024 0 0 0 0 2,152,236 3.6

Ulmus parvifolia 167,696 447,545 796,404 592,824 27,024 0 0 0 0 2,031,493 3.4 Prosopis velutina 231,593 515,095 833,159 309,740 128,588 0 0 0 0 2,018,176 3.4

Parkinsonia florida 82,426 447,365 916,091 394,215 59,191 0 0 0 0 1,899,289 3.2

Fraxinus velutina 74,686 202,434 756,164 502,819 36,801 17,389 0 0 0 1,590,292 2.7

Chiltalpa tashkentensis 49,402 533,909 857,098 127,795 0 0 0 0 0 1,568,204 2.6

Chilopsis linearis 526,278 541,300 368,086 54,891 0 0 0 0 0 1,490,554 2.5 Prosopis glandulosa 335,971 319,431 593,343 188,443 0 0 0 0 0 1,437,188 2.4

Acacia farnesiana 222,188 344,696 485,618 327,068 48,986 0 0 0 0 1,428,556 2.4

Fraxinus angustifolia 50,546 203,812 599,098 441,737 38,699 0 0 0 0 1,333,892 2.2


460,568 506,494 297,099 12,996 0 0 0 0 0 1,277,158 2.2

Phoenix dactylifera 0 0 5,940 631,018 468,127 9,744 3,601 0 0 1,118,430 1.9

Prosopis alba 149,947 141,623 475,797 233,896 33,008 0 0 0 0 1,034,271 1.7 Pinus roxburghii 439 7,354 155,219 546,355 117,582 0 0 0 0 826,949 1.4 Morus alba 393 576 2,374 106,788 227,932 190,959 151,253 0 0 680,275 1.1


DBH Class (in)


$ Prosopis chilensis 32,794 133,322 292,054 131,491 19,350 0 0 0 0 609,011 1.0

Olea europaea 13,510 162,605 313,771 36,822 0 0 0 0 0 526,708 0.9 Prosopis torreyana 35,568 128,740 224,855 88,807 34,698 0 0 0 0 512,668 0.9

Gleditsia triacanthos 14,764 84,430 387,069 0 0 0 0 0 0 486,264 0.8

Vitex agnus-castus 285,116 127,459 39,820 0 0 0 0 0 0 452,395 0.8

Robinia pseudoacacia 12,025 128,058 176,490 36,357 0 0 0 0 0 352,929 0.6

Prosopis species 11,895 106,654 109,279 59,989 0 0 0 0 0 287,816 0.5 Platanus wrightii 12,239 0 60,171 82,288 82,577 17,389 0 0 0 254,664 0.4

Pyrus kawakamii 0 62,134 122,334 58,777 0 0 0 0 0 243,245 0.4

Chamaerops humilis 709 85,221 56,886 71,781 0 0 0 0 0 214,597 0.4

Prosopis pubescens 31,737 67,016 78,091 20,602 0 0 0 0 0 197,446 0.3

Fouquieria splendens 0 0 0 0 0 0 0 0 196,994 196,994 0.3

Yucca brevifolia 0 27,945 117,788 28,712 0 0 0 0 0 174,445 0.3 Fraxinus uhdei 1,614 19,310 78,889 71,651 0 0 0 0 0 171,465 0.3 Olneya tesota 4,594 14,955 108,609 41,270 0 0 0 0 0 169,427 0.3 Rhus lancea 18,429 47,357 101,726 0 0 0 0 0 0 167,511 0.3 Washingtonia robusta 0 1,389 21,941 118,246 6,557 0 0 0 0 148,134 0.2

Other trees 370,573 570,686 775,112 381,799 62,032 37,135 95,739 3,480 0 2,296,554 3.9 Parkinsonia aculeata 4,265 21,135 66,323 36,515 0 0 0 0 0 128,238 0.2

Phoenix canariensis 961 0 0 41,841 23,245 9,298 51,139 0 0 126,483 0.2

Acacia aneura 48,886 61,863 9,704 0 0 0 0 0 0 120,452 0.2 Washingtonia filifera 0 636 11,376 32,136 23,334 27,837 2,320 3,480 0 101,118 0.2


DBH Class (in)


$ Acacia greggii 44,065 26,558 11,377 14,356 0 0 0 0 0 96,357 0.2 Olea europaea 'Swan Hill' 30,299 15,786 50,194 0 0 0 0 0 0 96,278 0.2

Pinus pinea 0 3,626 55,213 24,490 0 0 0 0 0 83,329 0.1 Cercidium praecox 1,589 35,198 39,820 0 0 0 0 0 0 76,607 0.1

Brachychiton populneum 4,072 38,824 32,459 0 0 0 0 0 0 75,355 0.1

Eucalyptus microtheca 24,373 1,813 5,689 43,068 0 0 0 0 0 74,943 0.1

Pyrus calleryana 340 16,126 53,863 0 0 0 0 0 0 70,328 0.1 Populus fremontii 20,654 8,459 16,036 9,685 0 0 10,723 0 0 65,556 0.1

Sophora secundiflora 52,738 6,710 0 0 0 0 0 0 0 59,447 0.1

Fraxinus velutina 'Glabra' 810 3,631 22,726 32,115 0 0 0 0 0 59,282 0.1

Acacia constricta 5,259 35,731 17,066 0 0 0 0 0 0 58,055 0.1

Ligustrum lucidum 2,090 23,679 30,116 0 0 0 0 0 0 55,884 0.1

Koelreuteria paniculata 5,824 8,604 41,100 0 0 0 0 0 0 55,528 0.1

Plantanus occidentalis 1,832 3,603 11,449 29,970 0 0 0 0 0 46,854 0.1

Cercis canadensis 16,223 9,676 20,519 0 0 0 0 0 0 46,418 0.1

Brahea armata 0 4,744 25,776 15,848 0 0 0 0 0 46,368 0.1 Pinus brutia 0 6,459 5,847 31,230 0 0 0 0 0 43,536 0.1 Parkinsonia microphylla 12,672 25,667 5,130 0 0 0 0 0 0 43,469 0.1

Machaerium tipu 0 0 0 10,301 0 0 31,557 0 0 41,858 0.1

Prosopis juliflora 2,865 10,751 26,931 0 0 0 0 0 0 40,547 0.1 Quercus ilex 16,992 16,746 0 0 0 0 0 0 0 33,737 0.1 Prunus 4,442 16,904 11,121 0 0 0 0 0 0 32,468 0.1


DBH Class (in)


$ cerasifera Parkinsonia x 'Sonoran Emerald'

5,322 17,604 7,267 0 0 0 0 0 0 30,193 0.1

Eucalyptus camaldulensis 1,384 1,393 10,472 0 15,453 0 0 0 0 28,702 0.0

Quercus gambelli 0 0 10,260 18,411 0 0 0 0 0 28,671 0.0

Quecus shumardii 2,619 4,659 13,544 5,856 0 0 0 0 0 26,679 0.0

Quercus lobata 163 0 10,472 14,124 0 0 0 0 0 24,758 0.0 Cupressus glabra 853 1,497 12,425 7,348 0 0 0 0 0 22,122 0.0

Ulmus pumila 1,384 1,969 17,593 0 0 0 0 0 0 20,946 0.0 Lagerstroemia indica 2,215 18,276 0 0 0 0 0 0 0 20,492 0.0

Quercus muehlenbergii 2,930 11,865 4,747 0 0 0 0 0 0 19,542 0.0

Ebenopsis ebano 3,088 12,373 4,015 0 0 0 0 0 0 19,476 0.0

Melia azedarach 1,494 5,526 12,330 0 0 0 0 0 0 19,350 0.0 Acacia schaffneri 5,342 2,560 11,377 0 0 0 0 0 0 19,279 0.0

Arbutus unedo 170 17,599 0 0 0 0 0 0 0 17,769 0.0 Acacia salicina 0 14,032 2,531 0 0 0 0 0 0 16,563 0.0 Populus spp. 950 15,227 0 0 0 0 0 0 0 16,177 0.0 Salix gooddingii 2,013 0 1,692 10,301 0 0 0 0 0 14,006 0.0 Albizia julibrissin 1,324 0 11,121 0 0 0 0 0 0 12,445 0.0 Schinus molle 355 0 11,377 0 0 0 0 0 0 11,732 0.0 Pistacia vera 600 0 9,912 0 0 0 0 0 0 10,513 0.0 Prunus caroliniana 960 9,493 0 0 0 0 0 0 0 10,453 0.0

Sophora japonica 96 1,633 8,378 0 0 0 0 0 0 10,106 0.0

Cupressus sempervirens 0 9,279 0 0 0 0 0 0 0 9,279 0.0


DBH Class (in)


$ Quercus fusiformis 4,153 3,626 0 0 0 0 0 0 0 7,779 0.0

Acacia pendula 0 1,813 5,689 0 0 0 0 0 0 7,502 0.0 Trachycarpus fortunei 0 0 7,457 0 0 0 0 0 0 7,457 0.0

Quercus suber 355 1,280 5,689 0 0 0 0 0 0 7,323 0.0 Vauquelinia californica 1,315 0 5,689 0 0 0 0 0 0 7,003 0.0

Robinia ambigua 'Purple Rose'

5,438 1,500 0 0 0 0 0 0 0 6,938 0.0

Celtis occidentalis 1,319 2,289 2,901 0 0 0 0 0 0 6,510 0.0

Eucalyptus spp. 0 0 5,689 0 0 0 0 0 0 5,689 0.0 Juniperus spp. 0 0 5,689 0 0 0 0 0 0 5,689 0.0 Leucaena retusa 960 0 4,015 0 0 0 0 0 0 4,975 0.0 Celtis reticulata 4,722 0 0 0 0 0 0 0 0 4,722 0.0 Butia capitata 0 0 0 4,203 0 0 0 0 0 4,203 0.0 Quercus buckleyi (texana)

1,845 576 1,676 0 0 0 0 0 0 4,097 0.0

Eucalyptus papuana 1,905 1,813 0 0 0 0 0 0 0 3,718 0.0

Eucalyptus microcarpa 0 3,626 0 0 0 0 0 0 0 3,626 0.0

Salix exigua 3,275 0 0 0 0 0 0 0 0 3,275 0.0 Nicotiana glauca 0 1,813 0 0 0 0 0 0 0 1,813 0.0

Rhus ovata 0 1,813 0 0 0 0 0 0 0 1,813 0.0 Prunus spp. 0 1,613 0 0 0 0 0 0 0 1,613 0.0 Arecastrum romanzoffianum 0 0 1,270 0 0 0 0 0 0 1,270 0.0

Eucalyptus woodwardii 1,130 0 0 0 0 0 0 0 0 1,130 0.0

Callistemon viminalis 982 0 0 0 0 0 0 0 0 982 0.0


DBH Class (in)


$ Eucalyptus sargentii 960 0 0 0 0 0 0 0 0 960 0.0

Tamarix chinensis 819 0 0 0 0 0 0 0 0 819 0.0

Cercis canadensis texensis

819 0 0 0 0 0 0 0 0 819 0.0

Ficus carica 819 0 0 0 0 0 0 0 0 819 0.0 Zelkova serratta 163 576 0 0 0 0 0 0 0 739 0.0 Fraxinus greggii 709 0 0 0 0 0 0 0 0 709 0.0 Eucalyptus gillii 525 0 0 0 0 0 0 0 0 525 0.0 Celtis sinensis 0 432 0 0 0 0 0 0 0 432 0.0 Cercis reniformis 409 0 0 0 0 0 0 0 0 409 0.0 Punica granatum 409 0 0 0 0 0 0 0 0 409 0.0

Malus spp. 409 0 0 0 0 0 0 0 0 409 0.0 Prunus armeniaca 409 0 0 0 0 0 0 0 0 409 0.0

Carya illinoinensis 355 0 0 0 0 0 0 0 0 355 0.0

Laurus nobillis 355 0 0 0 0 0 0 0 0 355 0.0 Celtis pallida 355 0 0 0 0 0 0 0 0 355 0.0 Caesalpinia cascalaco 250 0 0 0 0 0 0 0 0 250 0.0

Simmondsia chinensis 250 0 0 0 0 0 0 0 0 250 0.0

Xylosma congestum 250 0 0 0 0 0 0 0 0 250 0.0

Fraxinus americana junginger

231 0 0 0 0 0 0 0 0 231 0.0

Cercis orbiculata 170 0 0 0 0 0 0 0 0 170 0.0 Citywide Total $3,970,227 $9,741,792 $21,924,589 $17,096,647 $5,284,434 $775,341 $313,116 $3,480 $196,994 $59,306,619 100%

Documents

URBAN FOREST RESOURCE ANALYSISforestry.nv.gov/.../01/Henderson-Resource-Analysis... · City of Henderson, Urban Forest Resource Analysis ii December 2013. Tables . Table 1. Population